The definition of circa is about or approximately regarding dates.
An example of circa is the estimated date on an antique desk at a museum.
circa definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
about: used before an approximate date or figure: circa 1650
Origin: Classical Latin
circa definition by American Heritage Dictionary
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
preposition Abbr. c.
In approximately; about: born circa 1900.
Origin: Latin circā, from circum, around (probably on the model of adverbs like intrā, within), from circus, circle; see circle.
circa - Medical Definition
preposition Abbr. ca
In approximately; about.