diff --git a/entries/block.txt b/entries/block.txt
index 48e8bd2..3a8551d 100644
--- a/entries/block.txt
+++ b/entries/block.txt
@@ -3,5 +3,5 @@ block
 v. [common; from process scheduling terminology in OS theory] 1. vi. To
 delay or sit idle while waiting for something. We're blocking until everyone
 gets here. Compare busy-wait. 2. block on vt. To block, waiting for
-(something). Lunch is blocked on Phil's arrival.
-
+(something). Lunch is blocked on Phil's arrival. 3. A type of cryptographic
+cipher, "block cipher".