Encroach means in slang: To creep is the basic idea. (in Slang Dictionary, added by Blas Álvarez)
What else does Encroach mean?
Intruding on or approaching, particularly in a subtle or sneaky manner; moving beyond the bounds of customary boundaries. (in Slang Dictionary, added by Lucas Sáez)
Stealthily or gradually seize rights or possessions of another person. (in Merlin Dictionary)
To move beyond the limits of what is possible. (in Merlin Dictionary)