hy·dro·phane 
(hīdrə-fān′)
(hīdrə-fān′)n.
An opal that is almost opaque when dry but transparent when wet.
hy·dropha·nous (hī-drŏfə-nəs) adj.
- underpass
- underpay
- underpayment
- underperform
- underperformance
- underperformer
- underpin
- underpinning
- underplay
- underplot
- underpopulated
- underpopulation
- underprice
- underprivileged
- underproduce
- underproduction
- underproof
- underprop
- underran
- underrate
- underreact
- underreaction
- underreport
- underrepresent
- underrepresentation