OBSERVATION n.
on, with a clock; the right ascension of a star, with a transit instrument and clock; the sun's altitude, or the distance of the moon from a star, with a sextant; the temperature, with a thermometer, etc.
OPERA n.
either tragic or comic, of which music forms an essential part; a drama wholly or mostly sung, consisting of recitative, arials, choruses, duets, trios, etc., with orchestral accompaniment, preludes, and interludes, together with appropriate costumes, scenery, and action; a lyric drama.
ORATORIO n.
divine event, elaborately set to music, in recitative, arias, grand choruses, etc., to be sung with an orchestral accompaniment, but without action, scenery, or costume, although the oratorio grew out of the Mysteries and the Miracle and Passion plays, which were acted.
OUT adv.
nt, etc., in, or into, a state of freedom, openness, disclosure, publicity, etc.; as, the sun shines out; he laughed out, to be out at the elbows; the secret has leaked out, or is out; the disease broke out on his face; the book is out. Leaves are out and perfect in a month. Bacon. She has not been out [in general soci…