n. — British Columbia, Education
an alcohol-free party in celebration of high school graduation.
Type: 5. Frequency — Chart 1 shows that dry grad is distinctly Canadian by virtue of frequency. What is called in other places "safe grad", (see grad meaning 3), is called dry grad in only one Canadian province, that is, in British Columbia (see Chart 2). Thus the term is a good lexical marker of BC English.
See also: grad
Images:

Chart 1: Internet Domain Search, 19 Nov. 2016
Chart 2: Regional Domain Search, 19 Nov. 2016