Red-breasted.n. A small sylviine bird of Europe, Erithacus rubecula; the robin, or robin redbreast. See robin.n. The American robin or migratory thrush, Merula migratoria or Turdus migratorius. See robin.n. The red-breasted sandpiper, or knot, Tringa canutus. See robin-snipe.n. The red-bellied sunfish, Lepomis auritus.