enlist

Short definition from Wiktionary

Verb

1. 1
   To enter on a list; to enroll; to register.
2. 2
   To voluntarily join a cause or organization, especially military service.
3. 3
   To recruit the aid or membership of others.
4. 4
   To secure; to obtain.

Noun

1. 1
   One who is enlisted, usually in a military service.