Lewis & Short

conventĭcŭlum, i, n. dim. [conventus] (rare).

  1. I. An assembly, meeting, association: conventicula hominum, quae postea civitates nominatae sunt, Cic. Sest. 42, 91: plebei urbanae, id. Dom. 28, 74.
  2. II. A place of assembly, Tac. A. 14, 15: ritus Christiani, Amm. 15, 5, 31; 27, 3, 13; Arn. 4, 152; Lact. 5, 11, 10.