ClearAll

ClearAll[s1,s2,…] clears all values, definitions, attributes, defaults, options and messages for the symbols si.

ClearAll[patt1,patt2,…] clears all symbols whose names textually match any of the arbitrary string patterns patti.

ClearAll[{spec1,spec,…}] clears any symbols that are equal to or whose names match any of the speci.

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