13 letters
- postdoctorate20
- postembryonal26
- postembryonic28
- postemergence25
- postemergency27
- postepileptic26
- postgraduates20
- posttensioned19
- potentiations18
- potentiometer20
- precipitately25
- precollegiate23
- predesignated21
- predesignates20
- predestinated19
- predestinates18
- predetermined22
- predeterminer21
- predetermines21
- predominately24
- preexistences27
- prefabricated26
- prefabricates25
- preformulated25
- preformulates24
- preinterviews24
- premoistening23
- preponderated22
- preponderates21
- preregistered19
- prerequisites26
- presbyterates21
- presbyterials22
- presentencing24
- presterilized27
- presterilizes26
- presweetening23
- pretelevision22
- pretensioning21
- pretentiously21
- pretermission20
- pretermitting22
- preternatural19
- privatenesses21
- prizefighters32
- proconsulates22
- procrastinate20
- professorates19
- professoriate19
- progesterones19
- prognosticate22
- proportionate20
- prostatectomy24
- protectionism23
- protectionist20
- protectorates19
- protectorship24
- protectresses19
- proteinaceous21
- proteoglycans25
- protestations17
- proximateness27
- psychrometers26
- pteridologies20
- pteridologist20
- pteridophytes24
- pteridosperms23
- pyrheliometer24
- pyrocatechols27
- pyromorphites26
- pyrophosphate28
- pyrophyllites27
- pyrotechnical28
- pyrotechnists24
- quadrilateral26
- quadripartite27
- quadrumvirate32
- quadruplicate32
- quarterbacked34
- quarterfinals28
- quartermaster26
- quarterstaffs29
- quarterstaves27
- quincentenary31
- quintessences28
- quintuplicate32
- reaccelerated21
- reaccelerates20
- reappropriate22
- rearticulated19
- rearticulates18
- recapitulated22
- recapitulates21
- rechristening22
- reconcentrate21
- reconditeness19
- reconnoitered19
- reconsecrated21
- reconsecrates20
- reconsolidate19
- reconstituted19
- reconstitutes18
- reconstructed22
- recontaminate21
- redetermining21
- redintegrated18
- redintegrates17
- redistributed19
- redistributes18
- reencountered20
- reflectometer23
- refractometer22
- rehabilitated20
- rehabilitates19
- reincorporate20
- reinstatement18
- reintegrating19
- reintegration17
- reintegrative20
- reinterpreted18
- reinterviewed22
- reinvestigate20
- reinvigorated21
- reinvigorates20
- reiteratively20
- relatednesses16
- rematerialize26
- rencountering22
- reorchestrate18
- repletenesses18
- repristinated18
- repristinates17
- requisiteness24
- reregistering18
- respirometers19
- restauranteur16
- restaurateurs15
- resystematize27
- retentiveness19
- retentivities18
- reticulocytes23
- retransmitted18
- reupholstered21
- rhodochrosite21
- righteousness19
- saccharimeter24
- saccharometer24
- scatterations17
- scatterbrains20
- sceneshifters22
- scholasticate22
- schoolmasters22
- schoolteacher24
- scleroprotein21
- screenwriters20
- scriptwriters22
- semidiameters20
- semiliterates17
- semiparasites19
- sempiternally24
- sensitometers17
- sententiously19
- septentrional19
- sesquiterpene27
- sextuplicated29
- sextuplicates28
- sharpshooters20
- sinterability20
- siphonosteles20
- skateboarders21
- skateboarding24
- snollygosters20
- softheartedly22
- somnambulated26
- somnambulates25
- sonneteerings18
- sophisticated22
- sophisticates21
- soteriologies16
- southeasterly19
- southwesterly22
- spectrometers22
- speechwriters24
- spermatocytes24
- spermatophyte26
- spinsterhoods20
- sportscasters19
- sportswriters19
- statelessness15
- statelinesses15
- statesmanlike22
- statesmanship22
- stationmaster17
- steadfastness18
- steamrollered19
- steeplebushes23
- steeplechaser22
- steeplechases22
- stegosauruses17
- stenographers21