When used with orchids s/h usually refers to the use of an expanded clay product like AliFlor, Hydro Therm or many others. Semi Hydroponic is the bottom watering of a plant with the clay product absorbing the water up from a reservoir to the roots. True hydroponic is growing in water and semi is half way there absorbing water as needed.
It is also used more loosely to mean growing in hydroponic rock without the absorption although that technically is not semi-hydroponic.
I use hydroponic rock extensively but do not use the water reservoir often calling this incorrectly s/h.
You can find the abbreviations for orchid names at
http://www.orchids.mu/Glossary/Glossary_A.htm