i-adjective
too short; insufficient in length
Rare expression meaning something is physically too short or falls short of a required length. Often replaced by 短すぎる or 足りない in modern speech.
この布は寸が足りないから、別のを探そう。
This cloth is too short, so let's look for another one.
昔の人は「寸が足りない」と言ったが、今はあまり使わない。
People in the past said 'sun ga tarinai,' but it's not used much nowadays.