Commonly used in the British commonwealth countries, the term "batchmate" refers to a person who was in the same "batch" as you were in school, college, a military or administrative academy; or another intensive program where people get to know their cohorts quite well. The rough American equivalent is "classmate"; however, batchmate implies a closer sense of togetherness and bonding.
The act of taking a hit but not inhaling it, therefore wasting some of the substance you are smoking. Applies to vapes, joints, cigs, or any smokable drug.
Chris has no idea how to smoke, he keeps on bitchaling and wasting our weed!