reticent
reserved or silent.
tenuous
: Thin, weak, or lacking substance; flimsy or fragile.
vapid
Not showing interest or intelligence; dull or lacking flavor.
capricious
Given to sudden changes of mood.
garish
Excessively bright or showy in a way that is unpleasant.
profligate
Recklessly extravagant or wasteful
surreptitious
Done secretly or stealthily
Recalcitrant
Stubbornly resistant to authority; disobedient.
pedantic
overly precise.
diffident
shy or hesitant.