To sign bull, take your dominant hand, form the letter Y sign, and hold it up to your forehead, palm facing out. You are mimicking the horns of a bull on your forehead.
We also use the letter Y hand for signing cow, so don't confuse the two animals' signs. The 'Y' hand for cow is signed at the temple and using the tip of the thumb, whereas the 'Y' hand for bull is signed at the forehead, with the back of the hand touching the forehead flat.
Teach your baby or toddler the bull sign when you encounter a bull in their picture book or story book, a cartoon, or if you happen to visit a ranch and see one live.
This is a useful flash card taught best in conjunction with actual visits to a ranch or farm, or when encountering bulls in your baby's story books or cartoons.