Ineffectual, a.
Not producing the proper effect; without effect; inefficient; weak; useless; futile; unavailing; as, an ineffectual attempt; an ineffectual expedient. Pope. The peony root has been much commended, . . . and yet has been by many found ineffectual. Boyle.
Syn. -- Inefficient; useless; inefficacious; vain; fruitless; unavailing; futile. See Uselesss, Inefficacious.
Shades of meaning
Fernald has no entry of its own for ineffectual; he lists it under vain.
Where he writes about it:
That which is bootless, fruitless, or profitless fails to accomplish any valuable result; that which is abortive, ineffectual, or unavailing fails to accomplish a result that it was, or was supposed to be, adapted to accomplish. — from vain
Fruitless is more final than ineffectual, as applying to the sum or harvest of endeavor. — from vain