To enter; go inside (a place); to allow or have s.o. enter.
The N- prefix and -un imp. are used most often for entering when there is a risk or danger involved. The -um- infix is abilitative.
I couldn't enter the house at that wedding because there were way too many people there.
I'm not bold enough to enter people's houses when they aren't home lest I be called a thief.