Oboe

Oboe, a treble-sounding musical instrument of the reed class, to which the bassoon is reckoned the bass.

Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)

Oblates * Obelus
[wait for the fun]
Obadiah
Oban
Obeid
Obelisk
Ober-Ammergau
Oberlin, Jean Friedrich
Oberon
Obi
Objective
Oblates
Oboe
Obelus
O'Brien, William
O'Brien, William Smith
Obscurantist
Obsidian
Occam
Occasionalism
Oceania
Oceania
Oceanides