Cases of word usage

1) (an instance of) seeming to see something not actually present (hallucination)

2) a drug dependent person, pretending to be against war but actually thus finding reason to drink a lot and avoid any work; very lazy person; hipster (hippie)

3) concerned with useful results, the possibility of actually being done (and not theory or principles) (pragmatic)

4) a person who was actually present at an event and should, for this reason, be able to describe it; a person who gives evidence under oath in a law court (witness)