8 [not in progressive]formalto expect that something will happen or be true, and to base your plans on it:
The company's plan supposes a steady increase in orders.
WORD CHOICE: WORD CHOICE: suppose, guessIn spoken phrases, I suppose and I guess are used in the same way, but suppose is more usual in British English and guessin American English• I suppose that's his mum. • I guess you're right. • I suppose you can come if you want to. • I guess I'll go home now.• 'Should we sit here?' 'I suppose so.' • 'Isn't he coming?' 'I guess not.'GRAMMAR!! Do not say 'be suppose to do something'. Use be supposed to• You're supposed to take your shoes off. • He's supposed to be very clever.
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.