1. This world; the netherworld or world of the dead; the inferior portion of mankind.

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

• underwourld,
• underworked,
• uderworld,
• underwold,
• underwoood,
• innerworld,
• underword,
• underwired,
• undeworld,
• inderworld,
• undereorld,
• undwerworld,
• underworl,
• undreworld,
• underwolrd,
• undurworld,
• undarworld,
• underbord,
• underbaord,
• underework

• underwing,
• underpart,
• underpants,
• underclothed,
• underarm,
• understand,
• under fire,
• undersize,
• underlying,
• undergo,
• underage,
• undercover,
• undermanned,
• underfed,
• underseal,
• undertaker,
• underdevelop,
• underprice,
• undertone,
• underrate,
• underproduce,
• underbody,
• underlay,
• undersealed,
• underling,
• underboss,
• undershirt,
• underpay,
• undermine,
• underground,
• underwear,
• under way,
• underwriter,
• underdone,
• undersoil,
• undertow,
• undergird,
• underived,
• underquote,
• undergrad,
• undervalue,
• understood,
• understated,
• underpass,
• underdog,
• undershot,
• undergrow,
• underbrush,
• understudy,
• under arms,
• underact,
• understate,
• undertide,
• underfur,
• underbred,
• underbid,
• undershoot,
• underslung,
• undertake,
• underwood,
• undergraduate,
• underscore,
• underdressed,
• underline,
• underhanded,
• under it,
• underclass,
• Underdahl,
• undersign,
• underdown,
• underway,
• underbodice,
• undersized,
• understock,
• under that,
• undercoat,
• underfelt,
• underspent,
• underhung,
• underside,
• underbelly,
• undersea,
• underhill,
• undershrub,
• underdress,
• undercut,
• underspend,
• underwrite,
• underplay,
• undercoated,
• undereducated,
• underskirt,
• underneath,
• undersexed,
• undersell,
• underclassman,
• underwater,
• underframe,
• underhand,
• underpin,
• underlie,
• underhandedly,
• underfoot.

The adjective form of the word "underworld" is "underworldly".

The plural of the "underworld" can be the "underworlds".

The singular of the "underworld" can be the "underworld".