信手

zhuō zi shang yǒu yī zhī qiān bǐ tā ná qǐ lai zài xī mò zhǐ shang xìn shǒu huà le yī gè tóu xiàng

桌子上有一支铅笔，他拿起来在吸墨纸上信手画了一个头像。

There was a pencil on the table, and unconsciously he drew a head on the blotting-paper.