Out-of-bounds and Unapproachable

Out-of-bounds adjective - Outside the foul lines.

Unapproachable and out-of-bounds are semantically related. In some cases you can use "Unapproachable" instead an adjective phrase "Out-of-bounds".

Unapproachable adjective - Hard or impossible to get to or get at.

Out-of-bounds and unapproachable are semantically related. Sometimes you can replace phrase "Out-of-bounds" with "Unapproachable", this terms are similar.