h2

The ratio between genetic variance and phenotypic variance used by plant breeders in selecting for yield, resistance or other characteristics.

H2

acronym: hydrogen
Found on http://cdiac.ornl.gov/pns/acronyms.html#H

H2

Header 2 / Second half of the year, details ...
Found on http://www.cryer.co.uk/glossary/h/index.htm

H2

Hydrogen.
Found on http://www.youngco.com/young2.asp?ID=4&Type=3

h2

Halo 2
Found on http://www.noslang.com/dictionary/h/
No exact match found