define

UK: /dɪˈfaɪn/ US: /dɪˈfaɪn/ ,(di fīn′)

Inflections of 'define' (v): (⇒ conjugate)

defines

v 3rd person singular

defining

v pres p

defined

v past

defined

v past p

WordReference Random House Learner's Dictionary of American English © 2026

de•fine /dɪˈfaɪn/   v. [ ~ + obj], -fined, -fin•ing. 

1. to set forth the meaning of:
   His job was to define new words that were not yet in the dictionaries.
2. to explain or identify the nature of;
   describe:
   We had to define what our problems were before we could solve them.
3. to determine or fix the boundaries of;
   specify clearly:
   to define responsibilities.
4. to make clear the outline or form of;
   delineate:
   The black tree was clearly defined against a yellow background.

de•fin•er, n. [countable] See -fin-.

WordReference Random House Unabridged Dictionary of American English © 2026

de•fine  (di fīn′), v. -fined, -fin•ing. 
v.t. 

1. to state or set forth the meaning of (a word, phrase, etc.):
   They disagreed on how to define "liberal.''
2. to explain or identify the nature or essential qualities of;
   describe:
   to define judicial functions.
3. to fix or lay down definitely;
   specify distinctly:
   to define one's responsibilities.
4. to determine or fix the boundaries or extent of:
   to define property with stakes.
5. to make clear the outline or form of:
   The roof was boldly defined against the sky.

v.i. 

6. to set forth the meaning of a word, phrase, etc.;
   construct a definition.

• Latin dēfīnīre to limit, define, equivalent. to dē- de- + fīnīre; see finish
• Anglo-French, Old French definer to put an end to
• Middle English def(f )inen 1325–75

de•fin′a•ble, adj. 
de•fin′a•bil′i•ty, n. 
de•fin′a•bly, adv. 
de•fine′ment, n. 
de•fin′er, n. 
Synonyms

• 3. state, name, describe, detail, enumerate.

Collins Concise English Dictionary © HarperCollins Publishers::

define / dɪˈfaɪn/ verb (transitive)

1. to state precisely the meaning of (words, terms, etc)
2. to describe the nature, properties, or essential qualities of
3. to determine the boundary or extent of
4. (often passive) to delineate the form or outline of: the shape of the tree was clearly defined by the light behind it
5. to fix with precision; specify

Etymology: 14th Century: from Old French definer to determine, from Latin dēfīnīre to set bounds to, from fīnīre to finish

deˈfinable adjective

deˈfiner noun