un ‧ im ‧ pres ‧ sive /ˌʌnɪmˈpresɪv◂/ BrE AmE adjective
[ Word Family: noun : ↑ impression , ↑ impressionism , ↑ impressionist , ↑ impressiveness ; adjective : ↑ impressionable , ↑ impressive ≠ ↑ unimpressive , ↑ impressionistic , ↑ unimpressed ; adverb : ↑ impressively , ↑ impressionistically ; verb : ↑ impress ]
not as good, large etc as expected or necessary:
unimpressive test results