Adjective
2. without basis
3. without foundation
4. ill-founded
5. unfounded
6. unsupported
7. uncorroborated
8. unproven
9. empty
10. idle
11. unsubstantiated
12. unwarranted
13. unjustified
14. unjustifiable
15. without cause
16. without reason
17. without justification
18. unreasonable
19. irrational
20. illogical
21. misguided