The word you're after is sweepstake
battles
crevasse
Some eight letter words with the seventh letter S are:bigamistchildishdisguiseflourishgoldfishgoodnessinterestlanguishmotoristoptimismprincesssuitcase
Mammals is the word.
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The only 7-letter English words are farside (s is 4th letter) and fridges (s is 7th letter).
shortstops
satisfying
foodstalls
acrobaticsaerobaticsschematicskinematicspragmaticsasthmatics
Toothbrush