Noun first base has 3 senses
  1. first base - the base that must be touched first by a base runner in baseball
    --1 is a kind of
    base, bag
  2. first base, first - the fielding position of the player on a baseball team who is stationed at first base
    --2 is a kind of position
    --2 is a member of baseball team
  3. first base - the initial stage in accomplishing something; "we didn't get to first base with that approach"
    --3 is a kind of
    first step, initiative, opening move, opening