SYN- Meaning of SYN- in English [syn-] or sym- prefix [ME, fr. OF, fr. L, fr. Gk, fr. syn with, together with] 1: with: along with: together "synclinal" "sympetalous" 2: at the same time "synesthesia" Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012