What does it mean?

My boyfriend's English is pretty damn good; my Turkish, not so great yet. He's been helping me with the little I have learned, and I do my best to help him become more familiar with informal phrases and slang and words he just doesn't know. Sometimes I have to hit the thesaurus or dictionary.com to find words I can use to explain that I know he already understands.

Yesterday he asked me what "abstract" meant. Um, yeah - YOU try and explain that one.