mer·man 
(mûrmăn′, -mən)
(mûrmăn′, -mən)n.
A legendary sea creature having the head and upper body of a man and the tail of a fish.
[MER(MAID) + MAN.]
- overstock
- overstory
- overstrain
- overstress
- overstretch
- overstride
- overstrung
- overstuff
- oversubscribe
- oversubscription
- oversupply
- overt
- overtake
- overtax
- overtaxation
- over the counter
- over-the-counter
- over the hill
- over-the-hill
- over the hump
- over the moon
- over-the-top
- over the top
- over the transom
- overthrow