Osmaterium -ia: fleshy, tubular, eversible processes producing a penetrating odor, capable of being projected through a slit in the prothoracic segment of certain Papilionid caterpillars, and from openings elsewhere in the bodies of other forms. {Scanner's comment: currently the only spelling I can find is "osmeterium". This given spelling is almost certainly an error on someone's part. Not only do the earliest books that I can find spell it "osmeterium", but the Greek root is "osme".}
Osmosis: the tendency of liquids to pass or diffuse through a membrane or septum.
Osselet: = ossicle; q.v.
Ossicle: a small nodule of chitin resembling a bone.
Ossicula: small corneous pieces that serve in the articulation of the wings to the thorax.
Ostia: the slit-like openings of the heart.
Ostiolar canal: a marginal furrow leading from the ostiole.
Ostiole: in Heteroptera, the openings at the sides of meso- and meta- thorax, through which an odoriferous fluid is excreted.
Ostium: singular of Ostia; q.v.
-osus; an affix, signifying saturation, or the possession of the quality expressed in the stem word.