Sentence:  O Fortune, Fortune, all men call thee <WSD>fickle</WSD>, / If thou art <WSD>fickle</WSD>, what doſt thou with him / That is renown'd for faith? be <WSD>fickle</WSD> Fortune: / For then I hope thou wilt not keepe him long, / But ſend him backe. 
Meaning of the word marked with <WSD> tags:  Quick to change one's opinion or allegiance; insincere; not loyal or reliable.