vague

"an obscure turn of phrase"; "an impulse to go off and fight certain obscure battles of his own spirit"; "their descriptions of human behavior become vague, dull, and unclear"; "vague...forms of speech...have so long passed for mysteries of science";

"a dim figure in the distance"; "only a faint recollection"; "shadowy figures in the gloom"; "saw a vague outline of a building through the fog"; "a few wispy memories of childhood";

"an undefined term"; "undefined authority"; "some undefined sense of excitement"; "vague feelings of sadness"; "a vague uneasiness";