Dictionary.net

a child's plaything consisting of an imitation horsehead on one end of a stick; the child straddles it and pretends to ride

a topic to which on constantly reverts; "don't get him started on his hobbyhorse"

a child's plaything consisting of an imitation horse mounted on rockers; the child straddles it and pretends to ride

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.

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.

A stick with a horse's head, across which children sit; a wooden rocking horse; a character in old morris dances.