na-adjective
insensitive; inconsiderate; indelicate
Internet slang for a person or remark that lacks delicacy or consideration for others' feelings. Often used critically to describe blunt or tactless behavior.
wasei-eigo (Japanese-coined English), from non-deli(cacy)
彼のノンデリな発言にみんな引いてしまった。
Everyone was put off by his insensitive remark.
あの人はノンデリすぎて、友達をよく怒らせる。
That person is so tactless that they often upset their friends.