The interference of one black piece by another like moving one on the same line (if the pieces are on different lines, it is a Holzhausen).
ECHESSPEDIA
Quotes of the Day
In order to become a grandmaster class player whose understanding of chess is superior to the thousands of ordinary players, you have to develop within yourself a large number of qualities, the qualities of an artistic creator, a calculating practitioner, a cold calm competitor.
Alexander Kotov
I think I would beat Tal pretty easily. Fischer would be more difficult, but I think I could beat him too.
Magnus Carlsen
Time trouble is blunder time.
Alexander Kotov
Kasparov’s book are the best, as far as high level analyses are concerned.
Jan Timman 1991 NIC
Fischer wanted to prove that all world championship games after his victory were prearranged. He did not convince me.
Vishy Anand 2008