A "bubble hem" is a style of clothing where the hem of a garment, like a dress or a skirt, is gathered or pleated to create a puffy or rounded shape at the bottom. Full definition
Short flounced sleeves with bubble hem. (1stdibs.com)
I really am not a fan of bubble hems at all, and cry over the thought of how pretty this would have been with a normal skirt. (elementsofstyleblog.com)
«Avignon» Italian silk como shantung strapless ball gown with rouched bodice, full bubble hem and elegant hand crafted cascading flowers, Ines Di Santo (brides.com)