An adverbial onomatopoeia meaning to appear unexpectedly or pop up suddenly; also used for accidentally meeting someone by chance.
彼はひょっこり部屋に入ってきた。
He popped into the room unexpectedly.
山道でひょっこり昔の友人に会った。
I unexpectedly ran into an old friend on the mountain path.
窓からひょっこり顔を出す猫がかわいい。
A cat poking its head out of the window is cute.
長い会議中に、彼がひょっこり現れた。
He suddenly showed up in the middle of the long meeting.