ab·o·ma·sum 
(ăb′ō-māsəm)
(ăb′ō-māsəm)n. pl. ab·o·ma·sa (-sə)
The fourth division of the stomach in ruminant animals, such as cows, sheep, and deer, in which digestion takes place.
[New Latin abomāsum : Latin ab-, ab- + Latin omāsum, tripe; see OMASUM.]
ab′o·masal (-səl) adj.
- on the face of it
- on the fence
- on the fly
- on the front burner
- on the go
- on the ground
- on the heels of
- on the hoof
- on the horns of a dilemma
- on the house
- on the increase
- on the inside
- on the job
- on-the-job
- on the level
- on the line
- on the loose
- on the make
- on the march
- on the market
- on the mend
- on the money
- on the move
- on the nose
- on the off chance