Wiktionary
vb. (context informal intransitive English) To depart quietly, without being noticed.
Usage examples of "slope off".
It's cap-rock country, so usually where the land breaks off there's a drop of four to fourteen feet of sheer rock, then a steep slope off to the bottom, and you may go miles before you can find a spot to go down into the canyon, or a place to climb out.
A ledge should slope off to the right not far belowthough when it didn't, he was possessed by a sudden fear that he'd passed it when he let himself drop down to avoid the arrows.
There he seemed to revive somewhat, for he made it over the gate, and above the village he picked up his stick, and pointed down the slope off to the right.
Austin thirty miles to the southwest of the Sun King and Alamo over the continental slope off Yucatan.
At all stations the local tracks rise several feet towards the street and slope off in both directions, while the express tracks do this only at stations at which the faster trains stop.
He got you free and, if you want to slope off now and do your own thing, we'll never mention we ever met ya.
NUMA research vessel assigned to a sonar mapping project of the continental slope off southern Brazil.
He pointed at the open and gentle slope off the trail to their east.