It stands for "off topic", theoretically unrelated to boating. I don't know
if it's newsgroup tradition or not, but it's done primarily for people who
might become fatally annoyed when clicking on the following subject line,
only to find that it's unrelated to boating:

"Bush Banned from Wal Mart After Swallowing Anti-Theft Bar Code Tag"

Washington Sunday 10/19/03
Wal Mart has requested that President Bush refrain from a planned fund
raising visit to several of their rural Virginia stores, after he swallowed
the anti-theft tag from a newly purchased copy of the video game "Warlords
IV - Heroes of Etheria". White House sources say Bush mistook the
rectangular plastic bar code for a stick of free gum. Lee Scott, Wal-Mart's
Chief Operating Officer and Vice Chairman said he's concerned about Bush
repeatedly setting off security alarms, which might be overly challenging to
store employees. "Our security staff completes a rigorous 30 minute training
course, but even so, we're concerned about them tackling Mr. Bush and
getting into an unfortunate scuffle with secret service personnel", said
Scott. "The White House's physician assures me that the president's problem
should pass within 48 hours, after which time he's welcome in any of our
stores".

Checkpoint Systems is Wal Mart's supplier for RFID merchandise tags. A
spokesperson said they've provided the White House with a full list of their
clientele so the president can avoid those merchants for the time being.