hob·by·horse /ˈhɑbiˌhɔrs/
 木馬;搖馬;竹馬
 Hob·by Hob·by·horse n.
 1. A strong, active horse, of a middle size, said to have been originally from Ireland; an ambling nag.
 2. A stick, often with the head or figure of a horse, on which boys make believe to ride. [ Usually under the form hobbyhorse.]
 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. [Usually under the form hobby.]
    Not one of them has any hobbyhorse, to use the phrase of Sterne.   --Macaulay.
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 hobbyhorse
      n 1: a topic to which one constantly reverts; "don't get him
           started on his hobbyhorse"
      2: a child's plaything consisting of an imitation horse mounted
         on rockers; the child straddles it and pretends to ride
         [syn: hobby, rocking horse]