Otillåtlig, not allowed, illicit.
Otjenlig, unfit, improper, inconvenient.
Otreflig (person), unsociable.
Otro, unbelief, incredulity.
Otrogen, incredulous; false, infidel.
Otrolig, incredible, improbable, unlikely.
Otrygg, unsafe.
Otröstlig, inconsolable.
Otta, prime of day.
Ottesång, matins.