Optical
Tickle an opera singer

Optimism
The cheerful spirit that makes it possible for a kettle to whistle with boiling water up its nose

Optimist
(1) A hope addict
(2) A man who goes downstairs with a fish pole when he finds his basement flooded.
(3) One who spends his last dollar to buy a money belt.
(4) A person who goes into a restaurant with no money and figures on paying for his meal with the pearl he hopes to find in the oyster he plans to order.

Optometrist:
A person of vision. – Joseph Leff

Optometrist’s Office:
A site for sore eyes. – Joseph Leff

Optometrist’s Top Floor Office:
A vision aerie. – Joseph Leff

Opus:
An exclamation at the sight of infected tissue fluids. – Joseph Leff

Orange
A fruit with a lot of appeal.

Orate:
Six or seven… – Joseph Leff

Oratory:
Is he a Whig…? – Joseph Leff

Orchestra Banned From the Telly:
Too much sax and violins. – Joseph Leff

Ordain:
A Scandinavian could be a Swede, a Norwegian… – Joseph Leff

Ordinary Son:
An heir plain. – Joseph Leff

Ore:
(1) Mined-over matter.
(2) A load off one’s mine. – Joseph Leff

Organ Grinder
Monster with food processor

Oriental Fans
Chinese movie buffs.

Osmosis
How Moses introduced himself to Pharaoh.

Ottoman
A car mechanic

Ouch
The sound heard when two porcupines kiss.

Ouija:
How to say “yes” in French and German. – Joseph Leff

Out Of Bounds
An exhausted kangaroo

Out of Patience:
A retired doctor. – Joseph Leff

Out on a Limb:
Asleep on a branch. – Joseph Leff

Outclass:
A course in environmental studies. – Joseph Leff

Outrageous:
To have a bigger tantrum than we can. – Joseph Leff

Outright:
Win an essay contest. – Joseph Leff

Outside:
Won a groaning contest. – Joseph Leff

Outweigh:
Exit. – Joseph Leff