13 letters
- palynological27
- pantheistical23
- parasiticidal21
- parenthetical23
- pentobarbital24
- permutational22
- petrochemical28
- pharmacopeial28
- phenobarbital26
- philosophical28
- photochemical30
- phrenological26
- physiological27
- phytochemical32
- polyribosomal26
- postclassical24
- postembryonal26
- postinaugural22
- postulational20
- praxeological30
- prebiological26
- prehistorical22
- preindustrial20
- premenopausal25
- premillennial24
- prepositional21
- preternatural19
- prevocational25
- problematical27
- proctological26
- procuratorial21
- progressional20
- propositional21
- proprietorial20
- prosecutorial21
- psephological28
- psychological30
- pyrotechnical28
- quadrilateral26
- radiochemical26
- rarefactional21
- reformational21
- seismological23
- selenological22
- semiclassical24
- semiempirical26
- semipolitical24
- sensorineural17
- septentrional19
- silvicultural25
- sociocultural23
- somatological23
- speleological24
- stereological20
- stereotypical22
- streptococcal26
- substructural23
- supercolossal22
- supercriminal25
- supercritical24
- supernational20
- superpersonal22
- superphysical28
- superregional21
- suppositional22
- supranational20
- suprarational19
- synarthrodial20
- synecdochical29
- synecological26
- technological26
- temperamental24
- teratological20
- tercentennial20
- terminational19
- tetartohedral17
- topographical27
- toxicological30
- transactional19
- transcultural21
- transfusional20
- translational17
- transnational17
- transpersonal19
- tritheistical19
- typographical29
- ultracritical22
- ultraphysical26
- ultrarational17
- unconditional22
- undialectical24
- unexceptional30
- ungrammatical27
- unideological23
- unintentional19
- unsensational18
- unsentimental21
- unsubstantial21
- unsymmetrical27
- untheoretical21
- untraditional18
- ventriloquial30
- ventrolateral20
- vivisectional26
- xylographical34