Definition of “proposition” - Learner’s Dictionary

proposition

noun [ C ] uk us /ˌprɒpəˈzɪʃən/
OFFER

an offer or suggestion, usually in business:

an attractive/interesting proposition
IDEA

an idea or opinion:

[ + that ] the proposition that all people are created equal
PLAN

in the US, a formal plan that people accept or refuse by voting

(Definition of “proposition” from the Cambridge Learner's Dictionary © Cambridge University Press)