ac ‧ ro ‧ nym /ˈækrənɪm/ BrE AmE noun [countable]
[ Date: 1900-2000 ; Origin: acr- 'beginning, end' (from Greek akr- , from akros ; ⇨ ↑ acrobat ) + -onym (as in homonym ) ]
a word made up from the first letters of the name of something such as an organization. For example, NATO is an acronym for the North Atlantic Treaty Organization.