1.VerbTo make a short visit somewhere, on the way to another place, either same-day or overnight.
"It's a long drive across Texas, so we're going to stop off in Austin for a night.; Let's stop off at the supermarket for a second, we have already run out of milk.; I stopped off at Welwyn North and took some photos."
2.VerbTo fill (a part of a mould) with sand, where a part of the cavity left by the pattern is not wanted for the casting.