undiplomatic

not diplomatic or tactful / lacking sensitivity or the skill of dealing with others

Japanese Meaning

外交的でない、慎重さや対人スキルに欠ける / 相手への配慮に欠け、みすぼらしい対応をする

His undiplomatic comment during the summit caused an awkward silence.

彼の失礼な発言は首脳会談の最中に気まずい沈黙を生んだ。

Sense（1）

not diplomatic or tactful

Sense（2）

lacking sensitivity or the skill of dealing with others

more undiplomatic

（ comparative ）

most undiplomatic

（ superlative ）