The Collaborative International Dictionary of English v.0.48:
Thriftless \Thrift"less\, a. Without thrift; not prudent or prosperous in money affairs. -- Thrift"less*ly, adv. -- Thrift"less*ness, n. [1913 Webster]WordNet (r) 3.0 (2006):
thriftless adj 1: careless of the future