Not very good
suboptimal adjective
not of the highest standard or quality
poor adjective
used for saying that something is not as good as it should be
average adjective
not very good
limited adjective
not very good, or not very great in amount
inferior adjective
if something is inferior, its quality is not good
disappointing adjective
not as good as you had hoped for or expected
inadequate adjective
not enough, or not good enough for a particular purpose
undistinguished adjective
not very good or special
substandard adjective
not as good as you would normally expect, or not good enough to be accepted
unsatisfactory adjective
not as good as you had hoped