straight edge

Short definition from Wiktionary

Noun

1. 1
   A lifestyle and subculture that advocates abstinence from alcohol, tobacco and the usage of recreational drugs.
2. 2
   One who follows this lifestyle.
3. 3
   Alternative form of straightedge (“tool to check straightness”).

Adjective

1. 1
   Living one's life opposing or eschewing the use of substances such as alcohol, tobacco, and drugs.