triph·thong 
(trĭfthông′, -thŏng′, trĭp-)
(trĭfthông′, -thŏng′, trĭp-)n.
A compound vowel sound resulting from the succession of three simple ones and functioning as a unit.
[TRI- + (DI)PHTHONG.]
triph·thongal (-thôngəl, -thŏngəl) adj.
- counterdemonstrator
- counterespionage
- counterexample
- counterfactual
- counterfeit
- counterfeiter
- counterfoil
- counterforce
- counterglow
- counterinsurgency
- counterinsurgent
- counterintelligence
- counterintuition
- counterintuitive
- counterintuitively
- counterirritant
- counterirritation
- counterman
- countermand
- countermarch
- countermeasure
- countermine
- countermove
- countermovement
- counteroffensive