multitudinous
Existing in multitudes or great numbers; very numerous; innumerable.
The great impoſtume of the realme vvas dravvne / Euen to a head: the multitudinous ſpavvne / VVas the corruption, vvhich did make it ſvvell / VVith hop'd ſedition (the burnt ſeed of hell.)
Comprising a large number of features or parts; manifold, multiple, myriad; also, having a large number of forms.
[I]n a State ſo multitudinous, where ſo many flocks of people muſt be fed, it is impoſſible to haue ſome Trades to ſtand, if they ſhould not Lye.
Comprising a large number of features or parts; manifold, multiple, myriad; also, having a large number of forms. — Of a sound: made by many people.
From the whole extent of the invisible vale came a multitudinous intonation; it forced upon their fancy that a great city lay below them, and that the murmur was the vociferation of its populace.
Of a body of water, the sea, etc.: huge, vast; also, having innumerable ripples.
literary
VVill all great Neptunes ocean vvaſh this blood / Cleane from my Hand? no: this my Hand vvill rather / The multitudinous Seas incarnardine, / Making the Greene one, Red.
Where it comes from
Learned borrowing from Latin multitūdin- (the oblique stem of multitūdō (“great number (of people), multitude”)) + English -ous (suffix forming adjectives from nouns, denoting the presence of a quality in any degree (typically an abundance)). Multitūdō is derived from multus (“many; much”) (ultimately from Proto-Indo-European *mel- (“to be late; to worry”)) + -tūdō (suffix forming abstract nouns denoting a condition or state). By surface analysis, multitude + -in- (interfix used before Latinate suffixes appended to nouns ending with -itude or -tude) + -ous.
Adapted from the Wiktionary entry multitudinous (CC BY-SA 4.0).