氣球 qìqiú HSK4 balloon Origin Definitions Defs Strokes Stroke Words Sentences Sents 热气球 rèqìqiú hot-air balloon hot-air balloon; a balloon that rises because the air inside is heated and becomes lighter than the surrounding air测风气球 cèfēngqìqiú pilot balloon A balloon used to observe upper-air wind direction by tracking it from the ground with a theodolite.