diff --git a/groff/math.tmac b/groff/math.tmac
index dad08be..2a34ca7 100644
--- a/groff/math.tmac
+++ b/groff/math.tmac
@@ -23,6 +23,7 @@ define div '{ \[di] }'
 define grad '{ \[gr] }'
 define aleph '{ \[Ah] }'
 define forall '{ \[fa] }'
+define rot 'roman "rot"'
 define sen 'roman "sen"'
 define tan 'roman "tan"'
 define sec 'roman "sec"'