擲弾筒: grenade launcher

(offensive, Internet slang) Alternative form of 子供部屋おじさん

(offensive, Internet slang) a man whose age is greater than about thirty or forty who lives in one's child room and with one's parent(s).

single room

double room

(idiomatic) to have grown tense (of a situation); to have become critical (and to be on the verge of a major upheaval)

基礎的: fundamental, basic

奇跡的: miraculous

(computer science) steepest descent method

stagehand in kabuki and bunraku (who dresses fully in black)