permanent, a. [stable], immutable, durable, [imperishable], [unchangeable], [abiding], indestructible. Antonyms: impermanent, evanescent, ephemeral, [transient].
permeable, a. [penetrable], [pervious], pervadible. Antonym: impermeable.
permission, n. [consent], [allowance], [license], [leave], [permit], authorization, [warrant]. Antonyms: [refusal], [denial], embargo, injunction, veto, prohibition, [resistance].
permit, v. [allow], consent to, suffer, [tolerate], [let], [authorize], [indulge], [license], empower. Antonyms: [refuse], disallow, [prohibit], [resist].
permit, n. [warrant], [license], [leave], [permission].
pernicious, a. [deleterious], [harmful], [noisome], baleful, [vicious].
pernickety, a. (Colloq.) [finical], [particular], [fastidious], [fussy].
perpendicular, a. [upright], [vertical]. Antonyms: horizontal oblique.
perpetual, a. See everlasting.
perplex, v. [bewilder], [puzzle], [pose], [confuse], [mystify], distract, disconcert, [entangle].