Source : Webster's Revised Unabridged Dictionary (1913)

Resistless \Re*sist"less\, a.
   1. Having no power to resist; making no opposition. [Obs. or
      R.] --Spenser.

   2. Incapable of being resisted; irresistible.

            Masters' commands come with a power resistless To
            such as owe them absolute subjection. --Milton.
      -- {Re*sist"less*ly}, adv. -- {Re*sist"less*ness}, n.

Source : WordNet®

resistless
     adj 1: impossible to resist; overpowering; "irresistible (or
            resistless) impulses"; "what happens when an
            irresistible force meets an immovable object?" [syn: {irresistible}]
            [ant: {resistible}]
     2: offering no resistance; "resistless hostages"; "No other
        colony showed such supine, selfish helplessness in
        allowing her own border citizens to be mercilessly
        harried"- Theodore Roosevelt [syn: {supine}, {unresisting}]