diff --git a/lib/libsys/getrlimit.2 b/lib/libsys/getrlimit.2
--- a/lib/libsys/getrlimit.2
+++ b/lib/libsys/getrlimit.2
@@ -84,6 +84,16 @@
 The maximum number of simultaneous processes for this user id.
 .It Dv RLIMIT_NPTS
 The maximum number of pseudo-terminals this user id is allowed to create.
+.It Dv RLIMIT_PIPEBUF
+The maximum total size of in-kernel buffers for bi-directional pipes/fifos
+that this user id is allowed to consume.
+The buffers for kernel FIFOs created on the first open of a filesystem
+object created by
+.Pq Xr mkfifo 2
+are also charged to the user ID of the process opening it,
+not the FIFO's filesystem owner.
+Despite somewhat unexpected, this is in fact fair, since user of the fifo
+is not necessary its creator.
 .It Dv RLIMIT_RSS
 When there is memory pressure and swap is available, prioritize eviction of
 a process' resident pages beyond this amount (in bytes).