DumpSave

DumpSave["file.mx",symbol] writes definitions associated with a symbol to a file in internal Wolfram System format. 

DumpSave["file.mx","context`"] writes out definitions associated with all symbols in the specified context. 

DumpSave["file.mx",{object1,object2,…}] writes out definitions for several symbols or contexts. 

DumpSave["package`",objects] chooses the name of the output file based on the computer system used. 

Please visit the official Wolfram Language Reference for more details and examples on core symbols.