Unprotect

Unprotect[s1,s2,…] removes the attribute Protected for the symbols si.

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

Unprotect[{spec1,spec2,…}] unprotects 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.