| Noun | 1. | first base - the base that must be touched first by a base runner in baseballbag, base - place that runner must touch before scoring; "he scrambled to get back to the bag" | |
| 2. | first base - the fielding position of the player on a baseball team who is stationed at first baseposition - (in team sports) the role assigned to an individual player; "what position does he play?" | |
| 3. | first base - the initial stage in accomplishing something; "we didn't get to first base with that approach" | |