@MurielSpriggs - The Equality Act does not define racism (or even mention it)! Racism is a long-standing concept that long predates 2010, and has nothing to do with UK law. In fact it seems rather arogant (and possibly racist) to say that it does!
You are correct, it doesn't. However, according to www.equalityhumanrights.com/en/advice-and-guidance/race-discrimination#act, it does state:
The Equality Act 2010 says you must not be discriminated against because of your race.
In the Equality Act, race can mean your colour, or your nationality (including your citizenship). It can also mean your ethnic or national origins, which may not be the same as your current nationality. For example, you may have Chinese national origins and be living in Britain with a British passport.
Race also covers ethnic and racial groups. This means a group of people who all share the same protected characteristic of ethnicity or race.
A racial group can be made up of two or more distinct racial groups, for example black Britons, British Asians, British Sikhs, British Jews, Romany Gypsies and Irish Travellers.
As racism is defined as discrimination on the basis of race (and in some dictionaries ethnic grouping), and the equality act states you should not be discriminated on the basis of race (which it defines as above), it is reasonable (in my opinion anyway) to use racism to describe the behaviour it states is illegal.