Crossword clues for the word: TERTIAN The word TERTIAN has appeared as an answer to at least 5 crossword clues on different crossword puzzles. Crossword clues for TERTIAN Showing 1 to 5 of 5 results Clue(s) "Treat, in effect, a kind of fever" Every 48 hours Every other day Fever to treat in 48-hour intervals Occurring every third day.