Manky
Manky is a commonly used word in British secondary schools, and is used to describe something nasty or disgusting. This can go from the school's spare kits or to that one scruffy girl who you just can't stand...
"Ew, Rebecca is actually manky. She doesn't brush her teeth!"
"These spare shorts are manky, I swear that the teachers don't wash them..."
"This burger is manky. The meat's not even fully cooked!"