na-adjective, noun
both eloquent and skilled; smooth-talking and dexterous
Describes a person who is both verbally fluent and manually capable, often with a nuance of being glib or slick. Can be used positively or critically depending on context.
彼は口八丁手八丁で、どんな仕事もそつなくこなす。
He is both eloquent and skilled, handling any job without a hitch.
口八丁手八丁の営業マンに説得されて、つい契約してしまった。
I was persuaded by the smooth-talking salesman and ended up signing the contract.
An idiomatic compound of 口 (mouth) + 八丁 (eight tools, implying skill) and 手 (hand) + 八丁, suggesting proficiency in both speech and manual tasks. The exact historical origin is uncertain, but it is a set phrase in modern Japanese.