i-adjective
not eating enough; still hungry
Literally means the amount eaten is insufficient; often implies the meal was not filling or satisfying.
給食だけでは食い足りない子もいる。
Some children find school lunch alone not enough to fill them up.
This amount isn't enough to satisfy my hunger.
i-adjective
unsatisfied; leaving something to be desired
Extended figurative use: a feeling that something is lacking or not fully satisfying, not limited to food.
説明が簡単すぎて食い足りない気がした。
The explanation was too simple and left me feeling unsatisfied.
映画は面白かったけど、ラストが食い足りなかった。
The movie was interesting, but the ending left something to be desired.