noun
person proud of their singing voice
Refers to someone who boasts about their singing ability, often in a lighthearted or self-deprecating way.
彼はカラオケに行くといつものど自慢になる。
He always becomes a proud singer when he goes to karaoke.
noun
amateur singing contest
Often used in the names of local or TV talent shows where ordinary people compete by singing.
An amateur singing contest was held at the neighborhood association.
カラオケ is the activity or venue; のど自慢 can refer to a person who loves to sing there or a contest format.
Compound of のど (throat/voice) and 自慢 (pride/boast). The contest sense likely derives from the idea of people proudly showing off their voices.