col·​li·​mate | \ ˈkä-lə-ˌmāt How to pronounce collimate (audio) \
collimated; collimating

Definition of collimate

transitive verb

: to make parallel collimate light rays

Keep scrolling for more

Other Words from collimate

collimation \ ˌkä-​lə-​ˈmā-​shən How to pronounce collimate (audio) \ noun

Did you know?

One might expect a science-y word like collimate to have a straightforward etymology, but that's not the case. Collimate comes from Latin collimare, a misreading of the Latin word collineare, meaning "to direct in a straight line." The erroneous collimare appeared in some editions of the works of ancient Roman statesman Cicero and scholar Aulus Gellius. The error was propagated by later writers-most notably by astronomers, such as Johannes Kepler, who wrote in Latin. And so it was the spelling collimate, rather than collineate, that passed into English in the 19th century.

Examples of collimate in a Sentence

Recent Examples on the Web But black holes produce their own radiation, especially high-energy X-rays and gamma-rays, which shoot out from the star in the form of tightly collimated... Newsweek, 14 Mar. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'collimate.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of collimate

1878, in the meaning defined above

History and Etymology for collimate

Latin collimatus, past participle of collimare, manuscript variant of collineare to make straight, from com- + linea line

Keep scrolling for more

Learn More About collimate

Time Traveler for collimate

Time Traveler

The first known use of collimate was in 1878

See more words from the same year

Listen to Our Podcast About collimate

Dictionary Entries Near collimate



collimating lens

See More Nearby Entries 

Statistics for collimate

Cite this Entry

“Collimate.” Dictionary, Merriam-Webster, Accessed 16 Oct. 2021.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

Keep scrolling for more

More Definitions for collimate


transitive verb
col·​li·​mate | \ ˈkäl-ə-ˌmāt How to pronounce collimate (audio) \
collimated; collimating

Medical Definition of collimate

: to make (as rays of light) parallel

Other Words from collimate

collimation \ ˌkäl-​ə-​ˈmā-​shən How to pronounce collimate (audio) \ noun


Test Your Vocabulary

Farm Idioms Quiz

  • cow coming home
  • What does 'poke' refer to in the expression 'pig in a poke'?
True or False

Test your knowledge - and maybe learn something along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!