躯 is a bound form (b.f.) meaning 'body' — it cannot stand alone as a word in modern Chinese. You'll only see it as part of compounds like 身躯 (body, stature), 躯体 (body, often in medical or biological contexts), and 躯干 (torso). When you learn these compounds, think of 躯 as the 'body' root that needs another character to form a usable word.