noun
: any of several hydrates Fe 2 O 3 . n H 2 O of ferric oxide that are capable of acting both as bases and weak acids : hydrated ferric oxide: as
a. : a reddish brown gelatinous precipitate obtained by adding an alkali to a ferric salt solution and often regarded as the trihydrate Fe(OH) 3
b. : a red to reddish brown crystalline oxide and hydroxide FeO(OH) occurring in nature as lepidocrocite