Sentence:  "That's nothing!" my companion repressed me, "anybody can <WSD>birl</WSD> a log. Watch this." / Roaring Dick for the first time unfolded his arms. With some appearance of caution he balanced his unstable footing into absolute immobility. Then he turned a somersault. 
Meaning of the word marked with <WSD> tags:  To cause (a floating log) to rotate by treading on it.