Use 'lackadaisical' to describe someone who seems uninterested or unwilling to put in effort. He had a lackadaisical stance on studying for finals.
Pro Tip 2/3
Informal Tone
'Lackadaisical' is moderate in formality, suitable for casual or creative contexts but not formal documents. Jenny's lackadaisical reply didn't impress the committee.
Pro Tip 3/3
Not Always Negative
While often critical, 'lackadaisical' can describe a laid-back quality that's positive in a relaxed setting. His lackadaisical vibe was perfect for the beach.