6 letter word: I P T S D U

6 letter word
Stupid

4 letter word
Tips
Suit
Stud
Spud
Spit
Puts
Pits
Dust
Dips

3 letter word
Ups
Tip
Sup
Sit
Sip
Put
Pus
Psi
Pit
Pis - plural of pi (the number)
Its
Ids - the id, psychological term
Dis
Dip