Mouth ulcer. Basically just a small open wound in your mouth that hurts like hell.
canker sores suck.....
by Bobby De Niro October 30, 2005
A canker sore is a sore on the inside of your mouth that you typically can't ignore, It suck ass
Lisa's a total slut no wonder she ended up with a canker sore.
by shanedashiz July 29, 2010
A person so annoying it's painful.
We were having the greatest night of our lives until those 2 canker sores showed up and they wouldn't leave. It always takes too long for a canker sore to go away.
by g_lo_t December 13, 2013