Fruitless, a.
1. Lacking, or not bearing, fruit; barren; destitute of offspring; as, a fruitless tree or shrub; a fruitless marriage. Shak.
2. Productive of no advantage or good effect; vain; idle; useless; unprofitable; as, a fruitless attempt; a fruitless controversy. They in mutual accusation spent The fruitless hours. Milton.
Syn. -- Useless; barren; unprofitable; abortive; ineffectual; vain; idle; profitless. See Useless. -- Fruit"less*ly, adv. -- Fruit"lness*ness, n.
Shades of meaning
Fernald has no entry of its own for fruitless; 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