The Collaborative International Dictionary of English v.0.48:
matrisib \matrisib\ n. One related on the mother's side. Syn: enate, matrikin, matrilineal kin, matrilineal sib. [WordNet 1.5]WordNet (r) 3.0 (2006):
matrisib n 1: one related on the mother's side [syn: enate, matrikin, matrilineal kin, matrisib, matrilineal sib]