Someone with good and many connections. Also, we call the person as "Madangbal" (마당발). It means a foot as big as a front yard at home. Madang is the front yard of a traditional Korean house. If a homemaker has "big hand"(큰 손), she is generous in her cooking and spending for others. Also, this "big hand"(큰 손) means for someone who control the biz largely such as property and stocks in the market. There was a lady whose name was Jang Yong Ja, was greatly involved in those markets to move the numbers up and down in 1980's.
예문: 영자씨는 정말 아는 사람도 많아요~ 어떤 문제가 생겨도 영자씨한테 부탁하면 해결이 되지요. 역시 "마당 발"이야...
장영자씨는 강남의 "큰 손"으로 유명했지요.
우리 어머니는 손님을 초대하면 음식을 많이 준비하세요 왜냐하면 어머니는 준비한 음식이 모자를까봐 늘 더 많이 준비하세요. "큰 손"이라니까요..!