define

Etymology

From Middle English definen, from Old French definer, variant of definir, from Latin dēfīniō (“limit, settle, define”), from dē + fīniō (“set a limit, bound, end”).

verb

1. To determine with precision; to mark out with distinctness; to ascertain or exhibit clearly.
   the defining power of an optical instrument
   Turbines have been around for a long time—windmills and water wheels are early examples. The name comes from the Latin turbo, meaning vortex, and thus the defining property of a turbine is that a fluid or gas turns the blades of a rotor, which is attached to a shaft that can perform useful work. 2013 July-August, Lee S. Langston, “The Adaptable Gas Turbine”, in (Please provide the book title or journal name)
2. (obsolete) To settle, decide (an argument etc.)
3. To express the essential nature of something.
   I define myself as a techno-anarchist.
   Your past mistakes do not define who you are.
   Cantor defined a one-to-one correspondence between the points of the square and the points of the line segment. Every point in the square was associated with a single point in the segment; every point in the segment was matched with a unique point in the square. 2013 May-June, Brian Hayes, “Crinkly Curves”, in American Scientist, volume 101, number 3, page 178
4. To state the meaning of a word, phrase, sign, or symbol.
   The textbook defined speed as velocity divided by time.
5. To describe, explain, or make definite and clear; used to request the listener or other person to elaborate or explain more clearly his or her intended meaning of a word or expression.
   Person 1: Is she good at math? Person 2: Define "good." If you mean if she is faster than the average middle schooler at multiplication, then yes. If you mean if she is able to do multivariable calculus, then no.
6. To demark sharply the outlines or limits of an area or concept.
   to define the legal boundaries of a property
   Few concepts are as emotionally charged as that of race. The word conjures up a mixture of associations—culture, ethnicity, genetics, subjugation, exclusion and persecution. But is the tragic history of efforts to define groups of people by race really a matter of the misuse of science, the abuse of a valid biological concept? 2012 March-April, Jan Sapp, “Race Finished”, in American Scientist, volume 100, number 2, page 164
7. (mathematics) To establish the referent of a term or notation.

noun

1. (programming) A kind of macro in source code that replaces one text string with another wherever it occurs.
   From the computer programming perspective, Java looks like C and C++ while discarding the overwhelming complexities of those languages, such as typedefs, defines, preprocessor, unions, pointers, and multiple inheritance. 1996, James Gosling, Henry McGilton, The Java Language Environment
   Anyone who has attempted to do OO programming in a conventional language using defines will find out that it is impossible to realize the benefits easily, if at all, without compiler support. 1999, Ian Joyner, Objects unencapsulated: Java, Eiffel, and C++, page 309