stack·up 
(stăkŭp′)
(stăkŭp′)n.
A deployment of aircraft circling an airport at designated altitudes while awaiting instructions to land.
- substitute
- substitution
- substitutional
- substitutionally
- substitutionary
- substitutive
- substrate
- substrative
- substratum
- substruction
- substructional
- substructural
- substructure
- subsumable
- subsume
- subsumption
- subsumptive
- subsurface
- subteen
- subtemperate
- subtenancy
- subtenant
- coarse-grained
- coarsely
- coarsen