hobbyn.[OE. hobi; cf. OF. hobe, hob, F. hobereau a hobby, a species of falcon. OF. hober to move, stir. Cf. Hobby a horse.] (Zol.) A small, strong-winged European falcon (Falco subbuteo), formerly trained for hawking.()n.[OE. hobin a nag, OF. hobin hobby; cf. hober to stir, move; prob. of German or Scand. origin; cf. Dan. hoppe a mare, dial. Sw. hoppa; perh. akin to E. hop to jump.]1. A strong, active horse, of a middle size, said to have been originally from Ireland; an ambling nag.(Johnson.)2. A stick, often with the head or figure of a horse, on which boys make believe to ride.()3. A subject or plan upon which one is constantly setting off; a favorite and ever-recurring theme of discourse, thought, or effort; that which occupies one's attention unduly, or to the weariness of others; a ruling passion.()Not one of them has any hobbyhorse, to use the phrase of Sterne. (Macaulay.)