大哥大

cell phone (bulky, early-model one) / brick phone / mob boss

see 大夫[dai4 fu5]

big; large; great / older (than another person) / eldest (as in 大姐[da4 jie3]) / greatly; freely; fully / (dialect) father / (dialect) uncle (father's brother)

eldest brother / big brother (polite address for a man of about the same age as oneself) / gang leader / boss

elder brother

Columbia University (abbr.)