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Webster 1828 Edition

Adj.

Wanting ground or foundation; wanting cause or reason for support; as groundless fear.

Not authorized; false; as a groundless report or assertion.

groundless ‎(comparative more groundless, superlative most groundless)

Without any grounds to support it; baseless.
- 2013, Delme Parfitt in Wales Online, Cardiff City 1 - 0 Swansea City: Steven Caulker heads Bluebirds to South Wales derby win (3 November 2013)
  At that stage any fears among home fans of a possession monopoly by Laudrup's side were proving groundless, with Cardiff having their fair share of the ball and territory.

baseless