This term means a variety of things depending on the user.  On this website we use the following definition:

Enlightenment is the permanent cessation of all mental afflictions.

The “state” of enlightenment is characterized by a continual abiding in “no-self” or the prajna paramita (perfection of wisdom).  The “state” of no-self or enlightenment is described by some as being without consciousness (Bernadette Roberts) and by others as being a pure consciousness state (Eckhart Tolle).  Presumably, the differences are due to different definitions of consciousness.

Synonyms: nirvana, gone to bliss, freedom, liberation