noun
stray hair; loose hair
Refers to individual strands of hair that have come loose from a hairstyle or updo, often seen as untidy or needing to be tucked back.
ポニーテールからほつれ毛が出ている。
There are stray hairs coming out of the ponytail.
ほつれ毛を耳にかける。
I tuck the loose hair behind my ear.
アホ毛 refers specifically to a single unruly strand sticking up, often on the top of the head, while ほつれ毛 is more general for any hair that has come loose from a style.
Compound of ほつれ (from verb ほつれる 'to come loose, to fray') and 毛 (け, 'hair'). The reading ほつれげ reflects rendaku voicing of け to げ.