i-adjective
Describes a thick, sticky texture that clings, like natto or heavy syrup. Often carries a slightly negative or emphatic nuance compared to 粘り強い.
この納豆はとても粘っこい。
This natto is very sticky.
手に粘っこいものがついてしまった
Something sticky got on my hands.
i-adjective
tenacious; persistent; stubborn
Used for a person's character or attitude that is annoyingly persistent or won't let go. More colloquial and negative than 粘り強い.
彼は粘っこくて、断ってもなかなか諦めない。
He's so persistent that even if you refuse, he won't give up easily.