Synonyms for Wasteful:

adj.

improvident (adjective)
uneconomical, thriftless.
inattentive (adjective)
careless.
inordinate (adjective)
overindulgent.
not economical (adjective)
incontinent, spendthrift, prodigal, immoderate, extravagant, reckless, lavish, wild, careless, pound-foolish, destructive, thriftless, Unthrifty, cavalier, uneconomical, improvident, profligate, profuse, liberal, squandering, overgenerous.
wasteful (adjective)
opulent, unconstrained, pound-foolish, overflowing, overindulgent, profuse, prodigal, extravagant, indulgent, profligate, thriftless, overabundant, immoderate, lavish, gluttonous, unrestrained.

n.

waster. extravagant (noun)
liberal, full-handed, squandering, reckless, without stint, out of bounds, wild, careless, improvident, Unthrifty, easy come easy go, overgenerous, dissipated, incontinent, cavalier, with money to burn.
wasteful (noun)
spendthrift, destructive, uneconomical, pound-foolish, uneconomic, profligate, extravagant, inefficient, prodigal.

Other synonyms:

waster. spendthrift
improvident, spendthrift.
Other relevant words:
extravagant, uneconomic, cavalier, squandering, inefficient, spendthrift, overgenerous, waster, reckless, Unthrifty, improvident, careless, uneconomical, liberal, wild, destructive, full-handed, incontinent, dissipated.

Usage examples for wasteful

  1. You are wasteful Abel." – The Miller Of Old Church by Ellen Glasgow
  2. I reduced the payments for legislation to a system, instead of the shameless, scandal- creating and wasteful auctioneering that had been going on for years. – The Plum Tree by David Graham Phillips