noun
keyboard warrior; Internet tough guy
Colloquial term for someone who acts tough or aggressive online but is meek in person. Derived from 内弁慶 (a person who is only bold at home).
彼はネット弁慶で、現実ではとてもおとなしい。
He's a keyboard warrior; in real life he's very meek.
ネット弁慶にならないように、ネットでも礼儀正しく振る舞おう。
Let's behave politely online too, so we don't become Internet tough guys.