1. to gradually worsen or decline in one's ability, expertise, or proficiency in a particular skill
His tennis skills deteriorated in skill after not playing for a year.
Suas habilidades de tênis deterioraram após um ano sem jogar.
2. to experience a loss of competence or technical ability over time
Musicians often deteriorate in skill if they stop practicing regularly.
Os músicos frequentemente pioram em competência se pararem de praticar regularmente.