impenetrable /im-penˈi-trə-bl/

1. Incapable of being penetrated
2. Impervious
3. Inscrutable
4. Occupying space exclusively (physics)

impenetrabilˈity noun

• well-turned
• well-upholstered
• well up in
• well-warranted
• well, well
• well-willer
• well-willers
• well-wish
• well-wished
• well-wisher
• well-wishers
• well-wishes
• well-wishing
• well woman
• well-woman clinic
• well-won
• willowiest
• willowing
• willowing-machine
• willowing-machines
• willowish
• willow pattern
• willow patterns
• willows
• willow tit