WordWeb Online

1. Of the highest quality, skill, etc.; very good or impressive
   - ace [informal], A-one [informal], crack [informal], first-rate, super, tiptop, topnotch [informal], top-notch [informal], tops [informal], A1 [informal], excellent, first-class, fantabulous [informal], splendid, ripping [Brit, informal], mean [informal], beezer [UK, archaic], lush [Brit, informal], stellar [informal], awesome [informal], brilliant, top-drawer
    
2. Distinguished from others in excellence
   "did outstanding work in human relations"; "an outstanding war record"
    
3. Having a quality that thrusts itself into attention
   "an outstanding fact of our time is that nations poisoned by anti semitism proved less fortunate in regard to their own freedom";
   - prominent, salient, spectacular, striking
    
4. Owed as a debt
   "outstanding bills"; "the amount still outstanding";
   - owing, undischarged
    
5. Of major significance or importance
   "Einstein was one of the outstanding figures of the 20th century";
   - great
    
6. Unresolved; not settled or finished
   "two issues remain outstanding"

See also: ace [informal], amazeballs [informal], awesomesauce [informal], beaut [Austral, NZ, informal], blinding [Brit, slang], brill [Brit, informal], conspicuous, crucial [slang], cushty [Brit, informal], def [slang], fab [Brit, informal], important, legit [US, slang], lit [US, slang], magic [Brit, slang], nang [Brit, slang], of import, phat [slang], rad [N. Amer, slang], radical [N. Amer, slang], righteous [US, slang], sick [N. Amer, slang], smokin' [slang], smoking [slang], socko [N. Amer, informal], stonking [Brit, informal], storming [Brit, informal], super [informal], super-duper [informal], superior, unpaid, wicked [slang]

Encyclopedia: Outstanding