Used in call centres to describe either ignoring a call completely or to hang up without explanation..
Derives from dropping something, ie having butterfingers, this then shortens to Butter
also can be used in the term Butterised.
"You coming on a break?"
"Im on a call but I'll Butterise it"
"I thought you were on a call"
"I was but I Buttered it"
"Shit 2 mins before the end of shift I feel a Butter coming on!"