giggle at (someone or something)
To utter a short laugh elicited by someone or something. I giggled at the baby's attempts to grab her feet. We giggled at the professor when his voice cracked, then quickly hid our faces when other people turned around to look at us.
giggle at someone or something
to snicker or chuckle at someone or something. Are you giggling at me? Fran giggled at the antics of the clown.