well-informed person; walking encyclopedia; extensive knowledge
Refers to a person who knows a lot about many things, or the quality of having broad knowledge. Often used in phrases like 物知り顔 (knowing look) or 物知りぶる (to act like a know-it-all).
He is really knowledgeable and answers any question.
祖父は植物に詳しい物知りだ。
My grandfather is a walking encyclopedia when it comes to plants.
He always talks as if he knows everything.
She's famous in her class for being a walking encyclopedia.
Rarely used kanji form; 識 carries a nuance of 'discernment' but is not common in modern writing.