throat·latch 
(thrōtlăch′)
(thrōtlăch′)n.
A strap passing under the neck of a horse for holding a bridle or halter in place.
- on tiptoe
- onto
- onto-
- on toes
- ontogenesis
- ontogenetic
- ontogenetically
- ontogenic
- ontogenically
- ontogeny
- ontological
- ontologically
- ontologist
- ontology
- on top
- on top of
- on top of the world
- on trial
- on/under pain of
- on/upon(one's) hands
- on/upon (one's) hands
- on/upon request
- on/upon the heels of
- on uppers
- onus