Contains

• aperture

  A natural opening in something.

• perforation

  A hole made in something; "a perforation of the eardrum".

• bullet hole

  A hole made by a bullet passing through it.

• knothole

  A hole in a board where a knot came out.

• ozone hole

  An area of the ozone layer (near the poles) that is seasonally depleted of ozone.

• bolt-hole

  A hole through which an animal may bolt when pursued into its burrow or den.

• leak

  An accidental hole that allows something (fluid or light etc.) to enter or escape; "one of...

• rathole

  A hole (as in the wall of a building) made by rats.

• cranny

  A small opening or crevice (especially in a rock face or wall).