15 letters
- postmillenarian25
- premillenarians25
- premillennially29
- preterminations23
- primitivenesses26
- promiscuousness27
- prostatectomies24
- psychochemicals37
- psychotomimetic34
- pusillanimities25
- radiochemically31
- recommissioning28
- recontaminating26
- recontamination24
- redetermination21
- retransmissions20
- schistosomiases23
- schistosomiasis23
- semiabstraction25
- semicentennials25
- semicolonialism27
- semicrystalline26
- semicylindrical30
- semidocumentary29
- semilogarithmic29
- semipornography31
- semiretirements22
- semisubmersible29
- semiterrestrial19
- semitranslucent25
- semitransparent23
- silversmithings28
- splenectomizing38
- squeamishnesses31
- stereochemistry25
- suboptimization35
- sympathectomies31
- sympathomimetic34
- tachyarrhythmia31
- thermochemistry30
- thermodynamical31
- thyroidectomies26
- toastmistresses18
- tonsillectomies24
- transaminations21
- transilluminate23
- transmigrations22
- transmissometer22
- trypanosomiases24
- trypanosomiasis24
- ultramicroscope29
- ultramicrotomes26
- uncompromisable33
- unfamiliarities24
- uniformitarians24
- unmitigatedness24
- verisimilitudes25