1.Definition: based primarily on surmise rather than adequate evidence

"The supposed reason for his absence"

Related Adjective(s):conjectural, divinatory, hypothetic, hypothetical, suppositional, suppositious, supposititious

2.Definition: doubtful or suspect

Related Adjective(s):alleged

3.Definition: mistakenly believed

"The supposed existence of ghosts"

4.Definition: required or under orders

"I'm supposed to be there at ten", "He was supposed to go to the store"