What Is The Symolic Meaning Of The Mockingbird In To Kill A Mockingbird?

As with all great writing, you can't find just one answer to the question of meaning in "To Kill a Mockingbird." However, there are ideas associated with the bird which are very important in the novel.

If you think about where it is first mentioned, Atticus is giving his children permission to shoot destructive birds, like jays, but adds "Remember, it's a sin to kill a mockingbird." Atticus, a liberal, tolerant man, doesn't use the word "sin" lightly. He explains it is because mockingbirds harm nobody, they just make lovely music. From this we can get the idea that Harper Lee chose the title so we keep this principle in mind - it is always wrong to harm those who have not harmed us. This idea can be applied to the treatment of specific characters in the novel - especially Boo Radley and Tom Robinson - and by extension to the glaring racial injustices and cruelties which are practised every day in Atticus's community. When he defends Tom in the trial, for instance, he is trying to prevent the townspeople from "killing a mockingbird" - that is, condemning an innocent man to death for no reason at all except prejudice.

Look the mockingbird is in the eye of the beholder you could totally argue it both ways between, Tom and Boo, but of course you must put into consideration that they both have their similarities tom for instance was shot physically and emotionally and boo was caged in like a mocking and left inside to hear the cruel "Shots"  taken with their words so in fact the symbolic mockingbird is either tom or boo not one or the other both have never done any harm,but are still being "shot" anyway

There is also another meaning of mockingbird in the title. The townspeople's opinions of Boo Radley and Tom Robinson are formed speaking by other townspeople. Few people listen to the own words of Boo Radley and Tom Robinson. They are hence mockingbirds, heard only through the songs of others.

I reckon the 'Mockingbird' in the novel refers to the black community in Maycomb
This is because if you read the novel carefully, you realise that aside from the Tom Robinson case, all the African Americans are well-mannered ,and , well, 'white.'
A mockingbird does not sing its own songs, but sings the songs of other birds, so in other words, it is copying the mannerisms of its neighbours.
The blacks are trying harder to be white that the whites living in maycomb, so therefore, they are the mockingbirds

The mockingbird is a symbol of innocence and mockingbirds share their own "music" of differences with everyone