ha ha ha; hee hee hee; chuckling
Onomatopoeic interjection representing a low, suppressed chuckle, often with a slightly mischievous or creepy undertone. Compare with ふふふ, which is lighter and more innocent.
See also: ふふふ
He chuckled eerily, 'gufufu.'
While thinking of a prank, I chuckle 'gufufu.'