Sentence:  One day he <WSD>sidles</WSD> up to a group, listens to the conversation for a moment, and actually puts in a remark. "I beg your pardon!" says one of the girls politely who has not heard his modest effort at conversation. For a moment Alexander remains rooted to the ground, he stammers out something unintelligible, the whole group turns and looks at him; this completes his confusion, he turns and <WSD>sidles</WSD> back to his seat, his face as hot as can be, and remains lost in a Latin grammersic 
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.