1. To approach someone or something in a quick, sneaky, and furtive manner so as to reach them or it without being noticed. Someone managed to steal up on Sneaky Pete, which I thought was all but impossible! The spy stole up on the guard tower and cut the power to the lights and security cameras.

2. To happen to or unfold before someone in a very quick, imperceptible manner. It seems like old age has stolen up on me in the blink of an eye. Where have all the years gone? It feels like the gentrification of this town stole up on those of us who've lived here our whole lives.