OPAQUEST
Adjective
opaquest
superlative form of opaque: most opaque
Usage notes
• Most opaque has been more common than opaquest for at least two centuries and 50 to 100 times more common in the last two decades.
Source: Wiktionary
OPAQUE
O*paque", a. Etym: [F., fr. L. opacus. Cf. Opacous.]
1. Impervious to the rays of light; not transparent; as, an opaque
substance.
2. Obscure; not clear; unintelligible. [Colloq.]
O*paque", n.
Definition: That which is opaque; opacity. Young.
Source: Webster’s Unabridged Dictionary 1913 Edition