clash

[1]	conflict , fight , battle , disagree , differ , argue , dispute , quarrel , squabble , feud , wrangle , cross swords
[2]	conflict , disharmonize , jar , be at odds/out of keeping
[3]	collide
[4]	jar , collide

[1]	crash , clang , clangor , clang , clank , clangour , clangoring , clangour , clank , crash
[2]	friction , collision , smash , (hostile) encounter , conflict , engagement , fight , battle , disagreement , difference , argument , dispute , altercation , quarrel , squabble
[3]	brush , encounter , skirmish