1. Without ground, reason, or warrant.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• froundless,
• vroundless,
• broundless,
• hroundless,
• yroundless,
• troundless,
• groundlees,
• groundlesss,
• groundlesse,
• grondless,
• groundles,
• groundness,
• frouncless,
• groundlesly,
• groundleve,
• groundlevle,
• grounderless,
• grondlesss,
• grondlessy,
• Groundlesnes

• ground cedar,
• grundyism,
• ground-shaker,
• ground wave,
• grounder,
• ground beef,
• ground fire,
• grindle,
• grandeur,
• groundhog,
• ground crew,
• ground-level,
• groundnut,
• groundmass,
• groundcover,
• ground noise,
• ground cherry,
• ground roller,
• ground cable,
• gruntle,
• ground fir,
• grunden,
• groundskeeper,
• grounds,
• grand lama,
• ground glass,
• groundfish,
• groundsman,
• ground beetle,
• Grandison,
• ground swell,
• groundspeed,
• grandee,
• ground snake,
• groundling,
• grounding,
• ground sloth,
• ground rule,
• ground stroke,
• greyhound,
• countless,
• grand mal,
• grandness,
• ground rose,
• Grandberry,
• granduncle,
• ground forces,
• groundball,
• grinder,
• Grindelia,
• granderson,
• ground state,
• groundsheet,
• ground tackle,
• ground ball,
• groundwork,
• ground pine,
• ground bass,
• ground ivy,
• ground out,
• ground level,
• grandiose,
• groundsel,
• grandson.

The adjective form of "groundless" is "baseless".

The plural form of the word "groundless" is "groundlesses". However, it is important to note that this plural form is not commonly used. In most cases, the word "groundless" is used as an adjective to describe plural nouns, such as "groundless fears" or "groundless accusations".

The singular form of the word "groundless" is "groundless". The word does not change in the singular form as it is an adjective that describes a noun.