per·i·ap·sis 
(pĕr′ē-ăpsĭs)
(pĕr′ē-ăpsĭs)n. pl. per·i·ap·si·des (-sĭ-dēz′)
The point at which an orbiting object is closest to the center of mass of the body it is orbiting.
- unprecedented
- unprecedentedly
- unpredictability
- unpredictable
- unpredictably
- unprejudiced
- unpremeditated
- unprepared
- unpreparedly
- unpreparedness
- unprepossessing
- unpretending
- unpretentious
- unpretentiously
- unpretentiousness
- unpriced
- unprincipled
- unprintable
- unproductive
- unproductively
- unproductiveness
- unprofessional
- unprofessionalism
- unprofessionally
- unprofitability