The letters in SUPPOSING make 144 words of two letters or more. The longest is SUPPOSING at 9 letters, and the highest-scoring is SUPPOSING at 14 points.
No other single word uses all 9 letters of SUPPOSING. SUPPOSING has 9 letters: 3 vowels and 6 consonants, worth 14 points before any board bonuses.
9-letter words 1
8-letter words 1
spousing11
7-letter words 8
oppugns12popguns12sopping12souping10sousing8spinous9supping12uppings12
6-letter words 12
gipons9gnosis7gossip9oppugn11opsins8pignus9pingos9pinups10popgun11posing9spuing9upping11
5-letter words 23
gipon8nisus5oping8opsin7pingo8pings8pinup9pions7pious7pisos7pongs8pungs8signs6sings6sinus5snips7snogs6snugs6songs6soups7spins7suing6using6
4-letter words 44
gins5gips7gnus5ions4nips6nogs5nous4onus4opus6pigs7ping7pins6pion6pips8piso6pois6pong7pons6pops8psis6pugs7pung7puns6pups8puss6sign5sing5sins4sips6snip6snog5snug5song5sons4sops6soup6sous4spin6spun6sung5suns4sups6unis4upon6
3-letter words 37
gin4gip6gnu4ins3ion3nip5nog4nos3nus3ons3ops5oui3pig6pin5pip7pis5piu5poi5pop7psi5pug6pun5pup7pus5sin3sip5sis3son3sop5sos3sou3sun3sup5uni3uns3upo5ups5
2-letter words 18
go3gs3in2is2no2nu2oi2on2op4os2pi4ps4si2so2ss2un2up4us2
Words are from our open word list and include some game-only words. Rude words are left out of this page; the unscrambler shows every valid word, lets you add blank tiles and filter by length.