slacker

Short definition from Wiktionary

Noun

1. 1
   One who procrastinates or is lazy; one who does not do their fair share or pull their own weight.
2. 2
   A person lacking a sense of direction in life; an underachiever.
3. 3
   A member of a certain 1990s subculture associated with Generation X.
4. 4
   A person who seeks to avoid military service.
5. 5
   A user of the Slackware Linux distribution.

Adjective

1. 1
   Comparative form of slack: more slack.