oscillate |ˈɑːsɪleɪt| — be undecided about something; waver between conflicting positions or courses of action

oscillating |ˈɑːsəˌletɪŋ| — having periodic vibrations

oscillation |ˌɑːsɪˈleɪʃn| — the process of oscillating between states

oscillator |ˈɑːsɪleɪtər| — generator that produces sonic oscillations or alternating current

oscillatory |ˈɑːsələˌtɔːrɪ| — having periodic vibrations

oscillograph |əˈsɪləˌɡraf| — a device for making a record of the wave forms of fluctuating voltages or currents

oscilloscope |əˈsɪləskəʊp| — electronic equipment that provides visual images of varying electrical quantities

oscitancy  — drowsiness and dullness manifested by yawning

oscitant |ˈɒsɪt(ə)nt| — showing lack of attention or boredom

osculant |ˈɒskjʊlənt| — Kissing; hence, touching or meeting; clinging.

oscular |ˈɑːskjələr| — Of or pertaining to the mouth.

osculate |ˈɑːskjəˌleɪt| — be intermediate between two taxonomic groups

osculation |ˌɒskjʊˈleɪʃən| — (mathematics) a contact of two curves (or two surfaces) at which they have a common tangent

osier |ˈəʊʒər| — flexible twig of a willow tree

Osiris |əʊˈsaɪərɪs| — Egyptian god of the underworld and judge of the dead; husband and brother of Isis; father of Horus

osmium |ˈɑːzmɪəm| — a hard brittle blue-grey or blue-black metallic element that is one of the platinum metals; the heaviest metal known

osmose |ˈɑːzməʊs| — (intransitive) To diffuse by osmosis.

osmosis |ɑːzˈməʊsɪs| — (biology, chemistry) diffusion of molecules through a semipermeable membrane from a place of higher concentration to a place of lower concentration until the concentration on both sides is equal

osmotic |ɒzˈməʊsɪs| — of or relating to osmosis

osprey |ˈɑːspreɪ| — large harmless hawk found worldwide that feeds on fish and builds a bulky nest often occupied for years

osseous |ˈɑːsɪəs| — composed of or containing bone

ossicle |ˈɑːsɪkəl| — a small bone; especially one in the middle ear

ossification |ˌɑːsəfəˈkeɪʃən| — the developmental process of bone formation

ossified |ˈɑːsəˌfaɪd| — set in a rigidly conventional pattern of behavior, habits, or beliefs

ossify |ˈɑːsɪfaɪ| — become bony

ossuary |ˈɑːsjʊəriː| — any receptacle for the burial of human bones

osteitis |ˌɑːstiːˈaɪtɪs| — inflammation of a bone as a consequence of infection or trauma or degeneration

ostensible |ɑːˈstensəbl| — appearing as such but not necessarily so

ostensibly |ɑːˈstensəblɪ| — from appearances alone

ostensory |ɑːˈstensəriː| — monstrance

ostentation |ˌɑːstenˈteɪʃn| — a gaudy outward display

ostentatious |ˌɑːstenˈteɪʃəs| — (of a display) tawdry or vulgar

osteoarthritis |ˌɑːstɪəʊɑːrˈθraɪtɪs| — chronic breakdown of cartilage in the joints; the most common form of arthritis occurring usually after middle age

osteography |ˌɑːstɪˈɑːɡrəfiː| — The scientific description of bones; osteology.

osteology |ɑːstiːˈɑːlədʒiː| — the branch of anatomy that studies the bones of the vertebrate skeleton

osteoporosis |ˌɑːstɪəʊpəˈrəʊsɪs| — abnormal loss of bony tissue resulting in fragile porous bones attributable to a lack of calcium; most common in postmenopausal women

ostler |ˈɑːslər| — someone employed in a stable to take care of the horses

ostracism |ˈɑːstrəsɪzəm| — the state of being banished or ostracized (excluded from society by general consent)

ostracize |ˈɑːstrəsaɪz| — expel from a community or group

ostracized |ˈɒstrəˌsaɪzd| — simple past tense and past participle of ostracize

ostrich |ˈɑːstrɪtʃ| — a person who refuses to face reality or recognize the truth (a reference to the popular notion that the ostrich hides from danger by burying its head in the sand)

Ostrogoth |ˈɑːstrəˌɡɑːθ| — a member of the eastern group of Goths who created a kingdom in northern Italy around 500 AD