synaeresis /sin-ēˈrə-sis/

1. The running together of two vowels into one or into a diphthong (phonetics)
2. The spontaneous expulsion of liquid from a gel (chem)

• pillar-root
• pillar-roots
• pillars
• pillar-saint
• Pillars of Hercules
• Pillars of Islam
• pillau
• pillbox
• pillboxes
• pill bug
• pill bugs
• pilled
• pillhead
• pillheads
• pillicock
• pillicocks
• pilling
• pillings
• pillion
• pillioned
• pillioning
• pillionist
• pillionists
• pillion-rider
• pillions