Source : Webster's Revised Unabridged Dictionary (1913)

Cliff \Cliff\ (kl[i^]f), n. [AS. clif, cloef; akin to OS. klif,
   D. klif, klip, Icel. klif, Dan. & G. klippe, Sw. klippa;
   perh. orig. a climbing place. See {Climb}.]
   A high, steep rock; a precipice.

   {Cliff swallow} (Zo["o]l.), a North American swallow
      ({Petrochelidon lunifrons}), which builds its nest against
      cliffs; the {eaves swallow}.

Source : WordNet®

cliff swallow
     n : North American swallow that lives in colonies and builds
         bottle-shaped mud nests on cliffs and walls [syn: {Hirundo
         pyrrhonota}]