Lewis & Short

con-grex, grĕgis, adj. (post-class.).

  1. I. Of the same herd or flock: equinis armentis, App. M. 7, p. 194, 41: aves, Sol. 2 dub. (al. congregatae).
    Hence,
  2. II. In gen., collected in flocks or multitudes: catervas, Auct. Pervig. Ven. 43: vulgo, Aus. Ep. 10, 21.
    With dat.: comessationibus, Tert. Poen. 11.
    1. B. Trop., close, intimate: aliquem congrege nexu tenere, Prud. contra Symm. 2, 634.