The definition of circum means around or about.
An example of circum is circumnavigate, which means to go completely around something.
around, about, surrounding, on all sides: circumnavigate, circumscribe
Origin of circum-; from Classical Latin circum, around, about, adv. accusative of circus: see circus
Around; about: circumlunar.
Origin of circum-Latin, from circum, around, accusative of circus, circle; see circle.