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
Petrosian would never have beaten me if he had played like that in 1963.
Mikhail Botvinnik 1966
First-class players lose to second-class players because second-class players sometimes play a first-class game
Siegbert Tarrasch
We will note the openings used by the participants of a nine-round match. The age of openings is considerably higher than the age of both rivals. Some opening positions could be analyzed by Steinitz when he was preparing to his match with Zukertort.
Mikhail Tal 1966 (Petrosian-Spassky match)
The Golden Age, when machines were weak and my hair was strong!
Garry Kasparov 2017
It isn’t important what comes off the board, but what stays on!
Yasser Seirawan