Tone-deafness; inability to perceive or reproduce musical pitch or rhythm accurately; a person who is bad at music.
彼はカラオケで音痴だとバレてしまった。
It became obvious that he is tone-deaf at karaoke.
専門医によると、本当に音痴（失楽音症）の人もいるという。
According to specialists, there are people who truly have amusia (tone-deafness).
自分は音痴だと思っていたが、練習で少し上手くなった。
I thought I was tone-deaf, but I improved a bit with practice.
Used as a suffix meaning 'having no sense of' or 'being hopeless at' (e.g., 方向音痴 = directionally challenged; パソコン音痴 = computer-illiterate).
彼女は方向音痴で、地図を見ても迷ってしまう。
She has a terrible sense of direction and gets lost even with a map.
僕は料理音痴だから、簡単なレシピでも焦がしてしまう。
I'm hopeless at cooking, so I burn even simple recipes.
パソコン音痴の祖父にスマホの使い方を教えた。
I taught my computer-illiterate grandfather how to use a smartphone.