Meaning of Ziwaru(じわる / ジワる)

Ziwaru(じわる) means “Something funny creeps up on me” or “It becomes funny slowly”.
It’s a slang.
Ziwaru(じわる) is an abbreviation for “Ziwaziwa Kuru(ジワジワ来る)”.
Ziwazaiwa(ジワジワ) is an onomatopoeia, it’s an expression of the situation “something is going slowly”.
Kuru(来る) means “coming”.
“Ziwaziwa Kuru(ジワジワ来る)” means same with ziwaru(じわる) or (ジワる).

So we use this word, when we find something funny.
The “sumething funny” takes a time just a bit until we get understand how it’s funny.

Example Conversation

A: Check out this video!
B: OK…
B: Mmm… what’s the point?
A: Watch carefully.
B: Oh, I got it!! Wow, It’s so crazy!! Super ziwaru!!

A: この動画見て!
B: おう。
B: え、なんなの？
A: よーく見てみ。
B: あ、わかった！あー、やべーなこれ、クッソじわる！