What is State Aid?

Legal Definition
State aid is the name given to a subsidy provided by a government. Under European Union competition law the term has a legal meaning, being any measure that demonstrates any of the characteristics in Article 107 of Treaty on the Functioning of the European Union, in that if it distorts competition or the free market, it is classed by the European Union as being illegal state aid. Measures which fall within the definition of state aid are considered unlawful unless provided under an exemption or notified by the European Commission.
-- Wikipedia
Legal Definition
Support or assistance furnished by the state to institutions, organizations or individuals, for a public purpose, or for the support of its needy citizens. See 55 Conn. 344, Ann. Cas. 1913B, 946, 82 Atl. 1030.
-- Ballentine's Law Dictionary