IPA: /ˈhɒbiˌhɔːs/
KK: /ˈhɑbiˌhɔrs/
An activity or interest that someone enjoys doing in their free time, often pursued for pleasure rather than for financial gain.
Gardening is her favorite hobbyhorse, and she spends every weekend tending to her plants.
Hobbyhorse is formed from "hobby" (from Middle English *hobby*, meaning a small horse or pony) and "horse" (from Old English *hors*, meaning horse). The term originally referred to a child's toy resembling a horse, which one could ride or play with, hence the playful connotation of the word.
Think of a small horse ('hobby') that children can play with, which helps you remember that a hobbyhorse is a toy horse.
No commonly confused words.