hair hanging down the back; pigtail; ponytail
Refers to hair that is tied or left to hang down the back, often in a single tail or two tails. The term can describe both the hairstyle and the hair itself.
She ties her long hair hanging down her back with a ribbon.
Hair hanging down the back goes well with a yukata.
Compound of 下げ (suspended, hanging) + 髪 (hair). The reading さげがみ is a straightforward kun'yomi combination.