anti- Look up anti- at Dictionary.com
word-forming element meaning "against, opposed to, opposite of, instead," shortened to ant- before vowels and -h-, from Old French anti- and directly from Latin anti-, from Greek anti "against, opposite, instead of," from PIE *anti- "against," also "in front of" (see ante-). It appears in some words in Middle English but was not commonly used in word formations until modern times.