Fishing term for the moment a fish takes the bait, felt as a tug on the line or seen as a movement of the float. Often used in phrases like 魚信がある (to get a bite) or 魚信を感じる (to feel a strike).
See also: 当たり (あたり)
After waiting a while, I got a bite on the rod.
When the float goes under, that's a strike.