Sentence:  “He hasn't learned the art of taking it gracefully,” said the Major. “But he shouldn't show temper. It's a sign of <WSD>coltishness</WSD> that I don't care for.” / “Ah, well, he's young,” said Daisy, with a sigh. “He'll get over that.” 
Meaning of the word marked with <WSD> tags:  The quality of being lively, playful and undisciplined.