(Canadian slang, noun) Individual eager to demonstrate knowledge or participate enthusiastically in school, church, seminars, etc. Like nerd, geek, brown-noser, smartypants, etc. but with more emphasis on willingness and enthusiasm, and less on social inadequacy, sycophancy, or natural ability.
Sally's classmates thought she was a keener because she always put her hand up in Chemistry, but her friends knew she had a crush on Mr. Smith.
A: I finished all the homework for next week.
B: Don't be such a keener! You're making the rest of us look bad!