Entries related to unofficial
prefix of negation, Old English un-, from Proto-Germanic *un- (source also of Old Saxon, Old Frisian, Old High German, German un-, Gothic un-, Dutch on-), from PIE *n- (source of Sanskrit a-, an- "not," Greek a-, an-, Old Irish an-, Latin in-), combining form of PIE root *ne- "not." Often euphemistic (such as untruth for "lie").
The most prolific of English prefixes, freely and widely used in Old English, where it forms more than 1,000 compounds. It underwent a mass extinction in early Middle English, but emerged with renewed vigor 16c. to form compounds with native and imported words. It disputes with Latin-derived cognate in- (1) the right to form the negation of certain words (indigestable/undigestable, etc.), and though both might be deployed in cooperation to indicate shades of meaning (unfamous/infamous), typically they are not.
It also makes words from phrases (such as uncalled-for, c. 1600; undreamed-of, 1630s; uncome-at-able, 1690s; unputdownable, 1947, of a book; un-in-one-breath-utterable, Ben Jonson; etc., but the habit is not restricted to un-; such as put-up-able-with, 1812). As a prefix in telegramese to replace not and save the cost of a word, it is attested by 1936.
late 14c., "performing a service" (a sense now obsolete); c. 1400, "required by duty," from Old French oficial "official; main, principal" (14c., Modern French officiel) and directly from Late Latin officialis "of or belonging to duty, service, or office," from Latin officium "service, kindness, favor; official duty, function, business; ceremonial observance," literally "work-doing," from ops (genitive opis) "power, might, abundance, means" (related to opus "work," from PIE root *op- "to work, produce in abundance") + combining form of facere "to make, to do" (from PIE root *dhe- "to set, put").
Meaning "pertaining to an office or official position" is from c. 1600. That of "derived from the proper office or officer," hence "authorized," is by 1854.
Others are reading
he participated in an unofficial capacity
a sort of unofficial mayor
an unofficial estimate
the early election returns are unofficial