heavy sweating; profuse sweat
Refers to sweating a lot, often in a visible or uncomfortable way. Commonly used in set phrases like 大汗をかく.
It was so hot I sweated heavily.
緊張して大汗をかいてしまった。
I got so nervous I broke out in a heavy sweat.
Compound of 大 (おお, 'big, great') + 汗 (あせ, 'sweat').