linchpin /linchˈ or linshˈpin/

1. A pin used to keep a wheel on its axle
2. A person or thing essential to a plan, organization, etc (figurative)

• abat-jours
• abator
• abators
• abattis
• abattises
• abattoir
• abattoirs
• abattu
• a battuta
• abature
• abatures
• abat-voix
• abaxial
• abaya
• abayas
• abb
• Abb.
• abba
• abbacies
• abbacy
• abbas
• Abbasid
• Abbaside
• abbatial
• abbess