1. Open to doubt or suspicion
   - doubtful, dubious, dubitable, doubtable

See also: questionable

• dauntingly
• dauntless
• dauntlessly
• dauntlessness
• dauphin
• Davalia bullata
• fellowship
• felly
• felo-de-se
• felon
• felonious
• felonry
• felony
• felsite
• felspar
• felt
• felt fern
• felt fungus
• felt hat
• felt tip
• felt up
• felt-tip pen
• felt-tipped pen
• felted
• felucca