Solemn, a.
Etymology: [OE. solempne, OF. solempne, L. solemnis, solennis, sollemnis, sollennis; sollus all, entire + annus a year; properly, that takes place every year; -- used especially of religious solemnities. Cf. Silly, Annual.]
1. Marked with religious rites and pomps; enjoined by, or connected with, religion; sacred. His holy rites and solemn feasts profaned. Milton. The worship of this image was advanced, and a solemn supplication observed everry year. Bp. Stillingfleet.
2. Pertaining to a festival; festive; festal. [Obs.] "On this solemn day." Chaucer.
3. Stately; ceremonious; grand. [Archaic] His feast so solemn and so rich. Chaucer. To-night we hold a splemn supper. Shak.
4. Fitted to awaken or express serious reflections; marked by seriousness; serious; grave; devout; as, a solemn promise; solemn earnestness. Nor wanting power to mitigate and swage With solemn touches troubled thoughts. Milton. There reigned a solemn silence over all. Spenser.
5 more senses
5. Real; earnest; downright. [Obs. & R.] Frederick, the emperor, . . . has spared no expense in strengthening this city; since which time we find no solemn taking it by the Turks. Fuller.
6. Affectedly grave or serious; as, to put on a solemn face. "A solemn coxcomb." Swift.
7. (Law)
Made in form; ceremonious; as, solemn war; conforming with all legal requirements; as, probate in solemn form. Burrill. Jarman. Greenleaf. Solemn League and Covenant. See Covenant, 2.
Syn. -- Grave; formal; ritual; ceremonial; sober; serious; reverential; devotional; devout. See Grave.
Shades of meaning
Fernald has no entry of its own for solemn; he lists it under awful.
Where he writes about it:
We speak of an exalted station, a grand mountain, an imposing presence, a majestic cathedral, a noble mien, a solemn litany, a stately march, an august assembly, the awful scene of the Judgment Day. — from awful