permafrost /pûrˈmə-frost/

Permanently frozen subsoil

• sinuously
• sinuousness
• sinuousnesses
• sinupallial
• sinupalliate
• sinus
• sinuses
• sinusitis
• sinusitises
• sinusoid
• sinusoidal
• sinusoidally
• sinusoids
• Siouan
• Sioux
• sip
• sipe
• siped
• sipes
• siphon
• siphonage
• siphonages
• siphonal
• Siphonaptera
• siphonapteran