blunder

Short definition from Wiktionary

Noun

1. 1
   A clumsy or embarrassing mistake.
2. 2
   A very bad move, usually caused by some tactical oversight.
3. 3
   Confusion; bewilderment; trouble; disturbance; clamour.

Verb

1. 1
   To make a big mistake, especially when it is careless or stupid.
2. 2
   To make a big mistake, especially when it is careless or stupid: To make a bad move, especially caused by tactical oversight.
3. 3
   To make a big mistake, especially when it is careless or stupid: To lose a piece due to having made a bad move [with the piece lost].
4. 4
   To make a big mistake, especially when it is careless or stupid: To overlook the possibility of, or end up in, a specified undesirable situation after making a bad move.
5. 5
   To move in an unsteady way.
6. 6
   To enter a place or become involved in a difficult situation by mistake.
7. 7
   To do or treat in a blundering manner; to confuse.