?Ambiguous command
A shortened version of a command that has more than one interpretation was specified on the command line. For instance, at the ftp prompt, you could type "qu," but that would be an ambiguous command because both "quit" and "quote" are valid commands in an Ftp session.
Retry the command, using a longer version of the command, for example, spelling the command name all the way out. To see a list of all the valid commands in a Telnet or Ftp session, type ? or HELP at the session command prompt.