oodles |ˈuːdlz| — a large number or amount

oof |uːf| — A sound mimicking the loss of air, as if someone's solar plexus had just been struck.

oolite |ˈəʊəlaɪt| — (geology) A rock consisting of spherical grains within a mineral cortex accreted around a nucleus, often of quartz grains.

oolitic |ˌəʊəˈlɪtɪk| — (geology) Made up of, or containing oolites

oology |əʊˈɑːlədʒiː| — the branch of zoology that studies eggs (especially birds' eggs and their size, shape, coloration, and number)

oolong |ˈuːlɒŋ| — Chinese tea leaves that have been partially fermented before being dried

oomph |ʊmf| — attractiveness to the opposite sex

oosperm  — (biology) The ovum, after fusion with the spermatozoon in impregnation.

ooze |uːz| — any thick, viscous matter

oozing |ˈuːzɪŋ| — the process of seeping

oozy |ˈuːzɪ| — leaking out slowly