An onomatopoeic adverb for giving a sharp, single glance; often used as 'じろりと'.
彼は私をじろりと見て、何も言わず席を立った。
He gave me a sharp look and stood up without saying anything.
不審な音がして、みんなじろりと辺りを見回した。
There was a strange noise and everyone glanced sharply around.
店員がじろりと私のカバンをのぞき込んだ。
The clerk peered into my bag with a sharp look.