mastiche, misteach, hematics, tachisme, megahits, hammiest, hematins, shipmate, mateship, atheisms.
Your query has returned 174 words, which include anagrams of atheism as well as other shorter words that can be made using the letters included in atheism.
The words in this list can be used in games such as Scrabble, Words with Friends, Wordscapes and other similar games.