Backlash has meaning in both socio-political and engineering contexts.
Socio-Political Backlash
In general backlash is a somewhat popular extreme negative reaction against something which had gained popularity, prominence, or influence. As such backlash is usually against something new or liberal, the old guard lashes back at something new. Occasionally movements are labelled backlashes against a movement which failed to gain much influence or prominence, in which case the label is simply an attempt to give the conservative movement credence. Sometimes it may be a manner of opinion, many feminists and other social liberals felt there was a conservative backlash during the 1980s, while others would say that feminism never was strong enough to be lashed back at.
However, there are several specific things related to backlash:
Engineering Backlash
In mechanical engineering, backlash is purposeful clearance between mating components:
