Source : Webster's Revised Unabridged Dictionary (1913)

Minacious \Mi*na"cious\, a. [L. minax, -acis. See {Menace}.]
   Threatening; menacing. [R.]

Source : WordNet®

minacious
     adj : threatening or foreshadowing evil or tragic developments; "a
           baleful look"; "forbidding thunderclouds"; "his tone
           became menacing"; "ominous rumblings of discontent";
           "sinister storm clouds"; "a sinister smile"; "his
           threatening behavior"; "ugly black clouds"; "the
           situation became ugly" [syn: {baleful}, {forbidding}, {menacing},
            {minatory}, {ominous}, {sinister}, {threatening}, {ugly}]