HSK 7-9
嘀咕
dígu动
to mutter; to feel apprehensive
他坐在角落小声嘀咕不停。
Tā zuò zài jiǎo luò xiǎo shēng dí gu bù tíng.
He sat in the corner muttering continuously.
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Appears across levels (7-9) in the HSK 3.0 word list.