2 sentences for 咕 (gū — mutter)

1. 他低着头咕了几句。

   tā dī zhe tóu gū le jǐ jù.

   He lowered his head and muttered a few words.

   Source: Dong Chinese Dictionary

2. 他一个人躲在角落里嘀咕，不知道在想什么。

   tā yī gè rén duǒ zài jiǎo​luò lǐ dí gū, bù zhī​dào zài xiǎng shén​me.

   He was muttering to himself in the corner, and I have no idea what he was thinking.

   Source: Dong Chinese Dictionary