being before all others with respect to time, order, rank, importance, etc., used as the ordinal number of one: the first edition; the first vice president.
2.
Music. highest or chief among several voices or instruments of the same class: first alto; first horn.
(often initial capital letter) being a member of the household or an intimate acquaintance of the president of the U.S. or of the governor of a state: the First Lady; Checkers, the first dog.
–adverb
5.
before all others or anything else in time, order, rank, etc.
6.
before some other thing, event, etc.: If you're going, phone first.
7.
for the first time: She first visited Atlanta in 1980.
8.
in preference to something else; rather; sooner: I'd die first.
9.
in the first place; firstly.
–noun
10.
the person or thing that is first in time, order, rank, etc.
11.
the beginning.
12.
the first part; first member of a series.
13.
Music.
a.
the voice or instrument that takes the highest or chief part in its class, esp. in an orchestra or chorus.
b.
a leader of a part or group of performers.
14.
Automotive. low gear; first gear: She shifted into first and drove off.
15.
the winning position or rank in a race or other competition.
[furst] 
) being a member of the household or an intimate acquaintance of the president of the U.S. or of the governor of a state: the First Lady; Checkers, the first dog.