Sentence:  Marta's gander was a magnificent snow-white bird: the object of terror to foxes, children and dogs. She had reared him as a gosling; and whenever he approached, he would let fly a low contented burble and <WSD>sidle</WSD> his neck around her thighs. 
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.