A mistaken or faulty construction.
A misconstrual or misinterpretation.
A misunderstanding or misinterpretation resulting from the use of the wrong meaning of a word that has multiple meanings.
An ungrammatical phrase.
A substantial mistake, usually causing problems for more people than just the person or group who made it.
A person who is mentally or emotionally damaged.
A person who often makes substantial mistakes; a bungler.