1. /T-T-Y/, /tit'ee/ n. The latter pronunciation was primarily ITS, but some Unix people say it this way as well; this pronunciation is not considered to have sexual undertones. 1. A terminal of the teletype variety, characterized by a noisy mechanical printer, a very limited character set, and poor print quality. Usage: antiquated (like the TTYs themselves). See also bit-paired keyboard. 2. [especially Unix] Any terminal at all; sometimes used to refer to the particular terminal controlling a given job. 3. [Unix] Any serial port, whether or not the device connected to it is a terminal; so called because under Unix such devices have names of the form tty*. Ambiguity between senses 2 and 3 is common but seldom bothersome. From Jargon Dictionary

2. An abbreviation for TeleType, which is used in Linux to mean terminal. For example, tty03 means terminal number 3. From Linux Guide @FirstLinux

3. controlling terminal From whatis

4. print the file name of the terminal connected to standard input From whatis