Abnormal Definition

ăb-nôrməl

adjective

Not typical, usual, or regular; not normal; deviant.

American Heritage

Not normal; not average; not typical; not usual; irregular, esp. to a considerable degree.

Webster's New World

Not conforming to rule or system; deviating from the usual or normal type. [First attested around the mid 19^th century.]

Wiktionary

Of or pertaining to that which is abnormal, in particular, behaviour that deviates from norms of social propriety or accepted standards of mental health. [First attested around the early 20^th century.]

Wiktionary

Synonyms:

Antonyms:

noun

A person or object that is not normal.

Wiktionary

Synonyms:

Other Word Forms of Abnormal

Singular:

abnormal

Plural:

abnormals

Alteration (influenced by ab–) of obsolete anormal from Medieval Latin anormālis blend of Late Latin abnormis (Latin ab- away from ab–¹) (Latin norma rule gnō- in Indo-European roots) anōmalus anomalous

From American Heritage Dictionary of the English Language, 5th Edition
ab- +‎ normal. First attested in 1835, replacing the earlier anormal and even earlier abnormous, from Latin abnormis (“departing from normal”), from either (ab- (“away from”) + norma (“rule, norm”)), or Ancient Greek ἀνώμαλος (anōmalos).

From Wiktionary