Both Jews and Gentiles . . . are all under sin. --Rom. iii. 9.

That led the embattled seraphim to war Under thy conduct. --Milton.

Who have their provand Only for bearing burdens, and sore blows For sinking under them. --Shak.
   (b) Denoting relation to something that exceeds in rank or degree, in number, size, weight, age, or the like; in a relation of the less to the greater, of inferiority, or of falling short.

Three sons he dying left under age. --Spenser.

Medicines take effect sometimes under, and sometimes above, the natural proportion of their virtue. --Hooker.

There are several hundred parishes in England under twenty pounds a year. --Swift.

It was too great an honor for any man under a duke. --Addison.

Note: Hence, it sometimes means at, with, or for, less than; as, he would not sell the horse under sixty dollars.

Several young men could never leave the pulpit under half a dozen conceits. --Swift.
   (c) Denoting relation to something that comprehends or includes, that represents or designates, that furnishes a cover, pretext, pretense, or the like; as, he betrayed him under the guise of friendship; Morpheus is represented under the figure of a boy asleep.

A crew who, under names of old renown . . . abused Fanatic Egypt. --Milton.

Mr. Duke may be mentioned under the double capacity of a poet and a divine. --Felton.

Under this head may come in the several contests and wars betwixt popes and the secular princes. --C. Leslie.
   (d) Less specifically, denoting the relation of being subject, of undergoing regard, treatment, or the like; as, a bill under discussion.

Abject and lost, lay these, covering the flood, Under amazement of their hideous change. --Milton.

Under arms. (Mil.)
   (a) Drawn up fully armed and equipped.
   (b) Enrolled for military service; as, the state has a million men under arms.

Under canvas.
   (a) (Naut.) Moved or propelled by sails; -- said of any vessel with her sail set, but especially of a steamer using her sails only, as distinguished from one under steam. Under steam and canvas signifies that a vessel is using both means of propulsion.
   (b) (Mil.) Provided with, or sheltered in, tents.

Under fire, exposed to an enemy's fire; taking part in a battle or general engagement.

Under foot. See under Foot, n.

Under ground, below the surface of the ground.

Under one's signature, with one's signature or name subscribed; attested or confirmed by one's signature. Cf. the second Note under Over, prep.

Under sail. (Naut.)
   (a) With anchor up, and under the influence of sails; moved by sails; in motion.
   (b) With sails set, though the anchor is down.
   (c) Same as Under canvas (a), above. --Totten.

Under sentence, having had one's sentence pronounced.

Under the breath, with low voice; very softly.

Under the lee (Naut.), to the leeward; as, under the lee of the land.

Under the rose. See under Rose, n.

Under water, below the surface of the water.

Under way, or Under weigh (Naut.), in a condition to make progress; having started.

Source: Webster's Revised Unabridged Dictionary (1913)