1 theoretical, unapplied, notional, ideational, conceptual, metaphysical, unpractical, intellectual:
It is difficult to capture abstract ideas on paper.
2 non-representational, symbolic, non-realistic:
Museums began buying abstract art in the 1930s.
3 summary, epitome, synopsis, essence, digest, condensation, survey, conspectus, extract; outline, précis, résumé:
By reading the abstracts, you can determine which articles merit reading in full.
4 epitomize, abbreviate, digest, summarize, condense, shorten, abridge, cut, cut down, US synopsize:
The service abstracts articles that appear in scientific journals.