Answer: ooos

AnswerCrossword Clue
OOOS

Some tic-tac-toe winners

OOOS

'XXX's and --' (Trisha Yearwood country hit)

OOOS

Add these to go from millionaire to billionaire

OOOS
They turn millionaires into billionaires
OOOS
What's needed to go from millionaire to billionaire
OOOSThey turn millionaires into billionaires?