first base

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The first of the bases in the infield, counterclockwise from home plate.
• noun The fielding position occupied by the first baseman.
• noun Slang The first stage or step toward completion or success.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun baseball The base after home plate in a counter-clockwise path around a baseball infield.
• noun by extension Completion of the first phase of an activity.
• noun US, colloquial Kissing.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the base that must be touched first by a base runner in baseball
• noun the initial stage in accomplishing something
• noun the fielding position of the player on a baseball team who is stationed at first of the bases in the infield (counting counterclockwise from home plate)