1. Gentle utterance use to call someone's attention
   - ahem, hem 
2. Exclamation expressing doubt, deliberation, dissent, or hesitation
   - hum, ahem

Encyclopedia: Hmm

• Paraguayan
• Paraguayan monetary unit
• parainfluenza virus
• parakeet
• paralanguage
• paraldehyde
• paralegal
• paraleipsis
• paralepsis
• Paralichthys
• Paralichthys dentatus
• Paralichthys lethostigmus
• paralinguistic communication
• Paralipomenon
• paralipsis
• Paralithodes
• Paralithodes camtschatica
• parallax
• parallel
• parallel axiom
• parallel bars
• parallel circuit
• parallel interface
• Parallel Lives
• parallel of latitude