Definition of cut ins:
(v) :
To intrude or interrupt.
(v) :
To pull in front of another vehicle in traffic, especially to do so dangerously or unfairly.
(v) :
To join a queue in the middle, as opposed to at the back.
(v) :
(surfing) To begin riding a wave in front of someone else whose legitimate turn it is.
(v) :
To take up a portion of.
(v) :
When painting, to paint edges, corners, or trim in preparation for rolling larger areas.