COMMON If you strike a blow for something such as a cause or principle, you do something which supports it or makes it more likely to succeed. Her appointment as Prime Minister would strike a blow for women's rights in Poland. Aged 83 and still working, he is also striking a blow for older actors. The ruling struck a blow for free speech. Note: You can also say you strike a blow against something, meaning you succeed in weakening the harmful effect of something. `We have struck a major blow against online fraud,' claims Inspector Ian Woodward.