You can use using
in order to set an alias for a namespace or type. More detail can be found in here.
Syntax:
using <identifier> = <namespace-or-type-name>;
Example:
using NewType = Dictionary<string, Dictionary<string,int>>;
NewType multiDictionary = new NewType();
//Use instances as you are using the original one
multiDictionary.Add("test", new Dictionary<string,int>());