1. noun /sʌb/
a) A submarine.
We can get subs at that deli.
With the score 4 to 1, they brought in subs.
2. verb /sʌb/
a) To substitute for.
He never really made a contribution to the match, so it was no surprise when he was subbed at half time.
b) To work as a substitute teacher, especially in primary and secondary education.
He was subbed on half way through the second half, and scored within minutes.
3. preposition /sʌb/
Under.
Wikipedia foundation.