Sentence:  As the moon <WSD>sidles</WSD> up / Must she <WSD>sidle</WSD> up, / As trips the scared moon / Away must she trip, [...] 
Meaning of the word marked with <WSD> tags:  "In the intransitive sense often followed by" '''(up)''': to (cause something to) advance in a coy, furtive, or unobtrusive manner.