fly in the ointment UK /ˈflaɪ ɪn ði ˈɔɪntm(ə)nt/US /ˈflaɪ ən ði ˈɔɪn(t)m(ə)nt/ noun1 •Something (especially a minor thing) which ruins or spoils everything else, or makes it less pleasant; a nuisance or problem; a disagreeable or unpleasant detail.And yet, in truth, he was not then a child of God. His pride and uncharitableness, were flies in the ointment. — 1807 formsflies in the ointment