The word "bathythermograph" uses 16 letters: aabeghhhmoprrtty.
bathythermograph is a valid word in this word list. For a definition, see the external dictionary links below.
Try a search for bathythermograph in these online resources (some words may not be found):
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Words formed by adding one letter before or after bathythermograph (in bold), or to aabeghhhmoprrtty in any order:
Shorter words found within bathythermograph