Is “Diphthongising” a Scrabble word?
Yes
DIPHTHONGISING
Valid in at least one Scrabble dictionary
Valid in these dictionaries
SOWPODS / CSW
Scrabble UK & International
TWL / NWL
Scrabble North America
Large English Dictionary
General English word list
Meaning of Diphthongising
verb
1.To change to a diphthong, as by inserting or removing a vowel.
2.To become a diphthong.