verb (used with object)
to make different in some particular, as size, style, course, or the like; modify: to alter a coat; to alter a will; to alter course.
to castrate or spay.
verb (used without object)
to change; become different or modified.
Origin of alter
1350–1400; Middle English < Old French alterer < Late Latin alterāre to change, worsen, derivative of Latin alter otherRelated formsal·ter·er, nounhalf-al·tered, adjectivepre·al·ter, verb (used with object)re·al·ter, verbun·al·ter·ing, adjectivewell-al·tered, adjectiveCan be confusedaltar alter
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for alterer
Derived Formsalterable, adjectivealterably, adverbalterability, noun
to make or become different in some respect; change
(tr) informal, mainly US a euphemistic word for castrate, spay
Word Origin for alter
C14: from Old French alterer, from Medieval Latin alterāre to change, from Latin alter other
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Word Origin and History for alterer
late 14c., "to change (something)," from Old French alterer "change, alter," from Medieval Latin alterare "to change," from Latin alter "the other (of the two)," from PIE *al- "beyond" (see alias (adv.)) + comparative suffix -ter (cf. other). Intransitive sense "to become otherwise" first recorded 1580s. Related: Altered; altering.
Online Etymology Dictionary, © 2010 Douglas Harper