A thing that is worthless or useless; shit; wack; messed up; bullshit; unfair.
“My parents made me call home to check in with them every hours..it was so jank.”
“That book is jank, I didn’t like it at all.”
“Get that jank-ass shit outta here!” (Ok, this one is redundant, no?)
(Courtesy of my 5 year old neice and 8 year old nephew. Yes, they do use this word in kindergarten.)