Definition of first base
- plans never got to first base
a runner on first base
She hit a ground ball to first base.
He used to be a catcher, but now he plays first base.
baseball : the base that must be touched first by a base runner; also : the position of the player who defends the area around first base
What made you want to look up first base? Please tell us where you read or heard it (including the quote, if possible).