1. Trivial File Transfer Protocol TFTP is a bare-bones protocol used by devices that boot from the network. It is runs on top of UDP, so it doesn't require a real TCP/IP stack. Misunderstanding: Many people describe TFTP as simply a trivial version of FTP. This misses the point. The purpose of TFTP is not to reduce the complexity of file transfer, but to reduce the complexity of the underlying TCP/IP stack so that it can fit inside boot ROMs. Key point: TFTP is almost always used with BOOTP. BOOTP first configures the device, then TFTP transfers the boot image named by BOOTP. Key point: Many systems come with unnecessary TFTP servers. Many TFTP servers have bugs, like the backtracking problem or buffer overflows. As a consequence, many systems can be exploited with TFTP even though virtually nobody really uses it. Key point: A TFTP file transfer client is built into many operating systems (UNIX, Windows, etc.). These clients are often used to download rootkits when being broken into. Therefore, removing the TFTP client should be part of your hardening procedure. From Hacking-Lexicon

2. Trivial File Transfer Protocol: this is a simplified version of FTP without authentication and many other basic features. Often used for booting devices over a network. From Linux Guide @FirstLinux

3. Trivial file transfer program. Tftp is the user interface to the Internet TFTP (Trivial File Transfer Protocol), which allows users to transfer files to and from a remote machine. The remote host may be specified on the command line, in which case tftp uses host as the default host for future transfers. From Debian 3.0r0 APT