diff --git a/source/reference/program/mongostat.txt b/source/reference/program/mongostat.txt
index c551774722b..1948304e26b 100644
--- a/source/reference/program/mongostat.txt
+++ b/source/reference/program/mongostat.txt
@@ -256,6 +256,7 @@ average operations per second.
    UNK        unknown
    SLV        :term:`slave`
    RTR        mongos process ("router")
+   ARB        :term:`arbiter`
    =========  =========================
 
 Usage