#H5YR or #h5yr means High 5, You Rock!
It's the Umbraco community’s way of cheering for others for providing help or any kind of contribution to the Umbraco project. It's basically giving credit where credit is due.
The idea started at Codegarden 2010 during a talk by Alexander Kjerulf about happiness at work. Safe to say, the Umbraco community rapidly embraced the usage of #H5YR across online channels (especially Twitter!) and in person, like at Codegarden.
Why not give a fellow community member a #H5YR on Twitter?