From WordNet (r) 3.0 (2006) [wn]:
spa
n 1: a health resort near a spring or at the seaside [syn:
watering place, watering hole, spa]
2: a fashionable hotel usually in a resort area [syn: {resort
hotel}, spa]
3: a place of business with equipment and facilities for
exercising and improving physical fitness [syn: health spa,
spa, health club]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Spa \Spa\ (?; 277), n.
A spring or mineral water; -- so called from a place of this
name in Belgium.
[1913 Webster]