Moan, cry and complain are negative words which are used to express sadness whereas giggle is a positive word which means to laugh in a silly way. Therefore, it is the odd word out of the given options.
Word
Meaning
Moan
to make a long deep sound, usually because you are unhappy or suffering
Giggle
to laugh in a silly way
Cry
to produce tears from your eyes because you are unhappy or hurt
Complain
to say that you are annoyed, unhappy or not satisfied about somebody/something