definition a volatile bowel movement known to plug most toilets it contacts. It is known for it's distinct letter J shape. Although the cause is unknown many experts maintain that this is a result of witholding facility use for weeks upon time. So far remedies for the notorious 'J log' include eating a healthy supply of dates or other fiber rich foods can restore regularity to one's system.
"Chris do you know why the toilet isn't working?"
"Yeah someone J loged it, notice the J shape it has"