noun
A somewhat literary or formal noun describing a state of sluggishness, lack of energy, or unwillingness to act. Often used in written descriptions of mood or atmosphere.
午後の会議では、参加者に惰気が漂っていた。
During the afternoon meeting, a sense of listlessness hung over the participants.
彼は惰気に負けて、何も手につかなかった。
He gave in to indolence and couldn't get anything done.
Compound of 惰 (indolence, laziness) and 気 (spirit, mood). The exact historical derivation is uncertain, but the combination conveys a mood of sluggishness or lack of energy.