What constitutes someone being a fish

We often hear people say "oh that fish got so lucky" or "I bet that fish good"... and often people are calling someone a fish because of a suckout, misclick/bad play, etc etc, when that person could be a habitual winner or loser, but played bad that one hand.

And sometimes people refuse to accept that *gasp* they were outplayed on a hand... instead saying something like "oh, the fish got lucky" or they are a calling station (how could they call my 50 dollar bet on a A high flop with KK? Or maybe the person knew how I bet when I flopped an ace on a flop and when I didn't)

So, I'd like to see if we can some general criteria we can come up with. Can we determine if someone's a fish based on one hand? 5 hands? 10 hands? Entire session?

Is a fish someone who is loose pre-flop and passive on all streets? Or someone who chases bad odds every hand? Someone who makes awful bets? Someone who never makes a bet? Someone who is a nut peddler? Someone who raises with trash and hits? Someone who doesn't know when to stop firing bullets at a bluff? Is it the habitual loser? The maniac? The degenerate?

I'm curious to everyone's thoughts

Personally, I can label someone after an hr or so at the table. Shorter than that I just can’t tell. You can begin to see a pattern watching hands you are not in but the image invariably solidifies after being in a particular hand with him since you are so keen on the action of hands you are in. I am not saying I can label someone after one hand; just that I usually decide after being in ‘a’ hand with them. So the label is a culmination of lots of observations made over a period of time.

There are so many things that go into a read, you usually can’t choose just one.
Passivity is an element.
% of hands they see the flop.
% of time they will call a raise. If they ALWAYS call a raise, then yeah, that’s a tell.
Chasy-ness.
How they handle a whiffed AK raised hand.
Calling instead of raising with good hands?
Calling even with bad hands?
Etc…

One man's shark is another man's fish.

Actually, to extend the metaphor, a bad player who just enjoys poker could be defined differently as a fish, for a fish is swimming around looking for bait. Though the commen terms are 'sharks' and 'fish' not 'fishermen' and 'fish'. Maybe i'm just splitting hairs.
But the whiffed AK is a good one and how that's handled. You put in a hefty raise on the button, you got 3 callers, the flop doesn't remotely help you. Get over it. (Though I did call an AI bet on the river once with A high from an AKo hand, but that requires a specific read on a specific player, and I still consider myself lucky.)
My personal defintion would be thinking hands are much stronger than they actually are. Axo comes to mind. Without a miracle flop how are you gonna really work with that in a full ring?
And thinking things like a set are the ultimate slowplay hands. Not noticing what can hold up and what can't without some aggressive maneuvers. Not really grasping what a scary boards looks like, not taking into consideration all the possible outs. I imagine these are the true fish who'll take the bait.

I found a fish today...I know this belongs in the bad beats section but you asked about fish

(only including important players tho this was 10-max - there was one other caller who folded on the flop, thus the starting pot amount)

Hero ($10.55) is EP1 with :Ad: :Ac:
Villain ($12.25) is MP3

Hero raises to $0.50
Villain calls $0.50

Flop ($1.50)
:Td:

Hero bets $1.00
Villain raises $1.00
Hero raises $5.00
Villain calls $5.00

Turn
:Kh:

Hero is allin $4.05
Villain calls $4.05

River
:Tc:

Hero shows :Ad: :Ac:
Villain shows :Qc: :Th:

Villain wins.

I felt certain that this guy just had top pair from monitoring his prior play. Sure I could have gone allin on the flop as I committed myself there anyway, but I have little doubt that the result would have been the same. I was willing to payoff KT on the turn btw, with 8 outs to my name. I understand that he's pretty much committed on the turn as well so his call there isn't the worst ever with 5 outs...anyhow, there's one definition of a fish for you that I use - (routinely) can't lay down top pair to an obvious overpair. (who cont bluffs AK this hard from EP when reraised by LP?).

Based on poker tracker stats, I play against several "fish". They are not that bad actually. I think there is a difference between calling too much and folding too much. Both are bad, but people that fold too much are considered GOOD players based on Poker Tracker stats. This is not always the case.

Real "fish" are players that don't know what's going on. They don't even consider what their opponents are holding or know anything about odds.

I don't think I ever called someone a fish or a donk. I may have disliked someone at the table for personal reasons and said it once or twice a long time ago, or said it in a kidding way, but generally speaking I never call people fish or donk.

To me a fish is someone who makes consistently bad CALLS.

Is anyone else starting to cringe from the term "Donk" everytime someone says it? It's beginning to get REALLY annoying. I think anyone that even says "Donk" is a "Dork". It's old news. Let's start a new saying.

Two words:

BLUE HAT

'Donk' is soooo 2005

In general is fish is a weak passive player that can't help but to go broke in the long term. They losse to much by playing 2 many weak handa and draws. Also they play there strong hands 2 weakly.

.........

fish
(n) live one. A very loose player, usually implying one who loses regularly.

live one
(n phrase) 1. A very loose player, usually implying one who loses; a rich sucker. When a player gets up, before the remaining players find out whom the house is sending to replace him, the table clown may say, "Send us a live one." Also fish, pigeon, sometimes sucker

someone who is completely ignorant on how luck is such a big factor in them winning pot/s