He called the ball foul.

They should never play foul.

The water was fouled by oil.

There's a foul smell in the kitchen.

The ship's hull was covered in fouling.

The batter hit a foul ball.

The ball landed just outside the foul line.

There was evidence of foul play in the game.

His foul-up caused a lot of confusion.

The beekeeper discovered foulbrood in one of the hives.