18 letters
- superintelligences31
- supernaturalnesses26
- supersensitivities27
- supranationalities25
- thermoplasticities30
- thrombophlebitides36
- transmissibilities26
- transportabilities26
- triboelectricities28
- triboluminescences34
- trichloroethylenes30
- ultraconservatives32
- unaccountabilities32
- unassailablenesses26
- unattractivenesses28
- unchangeablenesses33
- uncharitablenesses30
- unconvincingnesses36
- ungrammaticalities32
- unpredictabilities31
- unprinciplednesses33
- unprofitablenesses31
- unreasonablenesses26
- unresponsivenesses29
- unrestrainednesses23
- unscrupulousnesses31
- unseasonablenesses26
- unsubstantialities26
- vaingloriousnesses28
- weatherproofnesses30