municipium (myoo-n[schwa]-sip-ee-[schwa]m), n. [Latin “free town”] Roman law. A self-governing town; specif., any community allied with or conquered by Rome and allowed to maintain certain privileges (such as maintaining separate laws called leges municipales). • The members of a municipium were also Roman citizens. Pl. municipia (myoo-ni-sip-ee-[schwa]).