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)

• eagle-flighted
• eagle-hawk
• eagle-hawks
• eagle-owl
• eagle-owls
• eagle-ray
• eagle-rays
• eagles
• eagle-sighted
• eagle-stone
• eaglet
• eaglets
• eagle-winged
• eaglewood
• eaglewoods
• eagling
• eagre
• eagres
• EAK
• ealdorman
• eale
• eales
• -ean
• ean
• EAN