Lewis Short
(verb) : ag-grĕgo (adg-), āvi, ātum, 1, grex, grego. *
* To bring or add to a flock: ADGREGARE: ad gregem ducere, Paul. ex Fest. p. 23 Müll.—Hence
* To add to something: se adgregare, to attach one's self to, to follow or adhere to (more rare than adjungere, and only in prose, but class.): si secum suos eduxerit, et eodem ceteros naufragos adgregaverit,Cic. Cat. 1, 12: filium eodem indicio ad patris interitum,to implicate in,id. Vatin. 10, 25: te semper in nostrum numerum adgregare soleo,to add to, reckon among,id. Mur. 7, 16: meam voluntatem ad summi viri dignitatem adgregāssem,had shown my zeal for the increase of his reputation,id. Fam. 1, 9: se ad eorum amicitiam, to join or ally themselves to, Caes. B. G. 6, 12; Vell. 2, 91: oppidani adgregant se Amphotero,Curt. 4, 5; and instead of se adgregare, the pass.: ne desciscentibus adgregarentur,Suet. Ner. 43.
Charlton T. Lewis, Charles Short, A Latin Dictionary