A looking inward; specifically, the act or process of self-examination, or inspection of one's own thoughts and feelings; the cognition which the mind has of its own acts and states
Empty space.
An available room in a hotel; guest house, etc.
An unoccupied position or job.
Lack of intelligence or understanding.
A blank mind, unoccupied with thought.
A defect in a crystal caused by the absence of an atom in a lattice