O’FFICE, s. a public charge or employment; agency; business

OLFA’CTORY, a. having the sense of smelling

O’LIVE, s. a plant producing oil; the fruit of the tree; the emblem of
    peace

O’MINOUS, a. exhibiting bad tokens of futurity

OMI’SSION, s. neglect of duty; neglect to do something

OMNI’POTENT, s. the Almighty

OMNIPRE’SENCE, s. unbounded presence

OMNI’SCIENCE, s. boundless knowledge; infinite wisdom

O’NSET, s. attack; storm; assault

O’PAL, s. a precious stone

O’PALINE, a. resembling opal

OPPORTU’NITY, s. convenience; suitableness of circumstances to any end

OPPRE’SS, v.a. crush by hardship or unreasonable severity; overpower;
    subdue

OPPRE’SSOR, s. one who harasses others with unreasonable or unjust
    severity

O’PTICAL, a. relating to the science of optics

O’PTICS, s. the science of the nature and laws of vision

O’PULENT, a. rich

O’RACLE, s. something delivered by supernatural wisdom; the place
    where, or persons of whom, the determinations of heaven are inquired

O’RAL, a. delivered by mouth; not written

O’RATOR, s. a public speaker; a man of eloquence

O’RBIT, s. a circle; path of a heavenly body

O’RCHARD, s. a garden of fruit trees

O’RCHIS, s. a kind of flowering plant

O’RDER, s. method; regularity; command; a rank or class; rule

O’RDINANCE, s. law; rule; appointment

O’RDINARY, a. established; regular; common; of low rank

O’RDNANCE, s. cannon; great guns

O’RGAN, s. natural instrument:  as the tongue is the organ of speech.  A
    musical instrument

ORGA’NIC, a. consisting of various parts co-operating with each other

O’RGANISM, s. organic structure

O’RIENT, a. eastern; oriental; bright; gaudy

ORI’GINAL, a. primitive; first

O’RNAMENT, v.a. embellish; decorate

OSCILLA’TION, a. the act of moving backward or forward like a pendulum

O’SSEOUS, a. bony; resembling bone

OSTENTA’TION, s. outward show; pride of riches or power

OSTRICH, s. a large bird

OTHERWISE, ad. in a different manner; by other causes; in other
    respects

OU’TLET, s. passage outward

OU’TSET, s. setting out; departure

OU’TWARD, a. external; opposed to inward.

OVERFLO’W, v.a. deluge; drown; overrun; fill beyond the brim

OVERTA’KE, v.a. catch anything by pursuit; come up to something going
    before