There are 9 15-letter words that end with 'iously'.
| conscientiously | inefficaciously |
| sanctimoniously | perspicaciously |
| subreptitiously | superstitiously |
| surreptitiously | unceremoniously |
| unpretentiously | |
Note: These 9 15-letter words that end with 'iously' are found from the USA & Canada version of the tournament Scrabble word list.