syn ‧ o ‧ nym /ˈsɪnənɪm/ BrE AmE noun [countable] technical
[ Date: 1400-1500 ; Language: Latin ; Origin: synonymum , from Greek , from synonymos 'synonymous' , from syn- ( ⇨ ↑ syn- ) + onyma 'name' ]
a word with the same meaning as another word in the same language ⇨ antonym
synonym for/of
‘Shut’ is a synonym of ‘closed’.