15 letters
- spectroscopists27
- spinthariscopes27
- subcontraoctave30
- superconducting31
- superconductive32
- superconductors28
- supercontinents25
- superconvenient29
- sycophantically33
- teleconferenced28
- teleconferences27
- toxicologically35
- ultracommercial30
- ultraconvenient27
- ultramicroscope29
- unaccommodating33
- uncommunicative35
- uncompassionate27
- uncomplainingly34
- uncomplimentary33
- uncomprehending33
- uncompromisable33
- unconcernedness27
- unconditionally27
- unconsciousness26
- uncontroversial26
- uncopyrightable33
- unreconstructed26
- vasoconstrictor26
- videoconference31
- viscoelasticity28