Real Dictionary

define
verb: If you define something, you show, describe, or state clearly what it is and what its limits are, or what it is like.

define in American English
to determine or set down the boundaries of
intransitive verb: to set forth the meaning of a word, phrase, etc.; construct a definition
transitive verb: to state or set forth the meaning of (a word, phrase, etc.)

define in British English
to state precisely the meaning of (words, terms, etc)