Question: I have defined multiple signatures in Gmail, but want to delete some of them.
How do I do it? I have figured out how to blank them out, but want to actually delete them so that they don't get selected by accident.

Answer: 
Blanking the field out is the only way and gives the result you are looking for. You can only have one signature per email address; not sure what you mean by selecting one accidently.
This seems to vary with different versions of Gmail. None of the answers I found were very helpful.

To delete a signature or change default do the following:

1. Click the cog on top right of mail screen and select *Settings*
2. Select the *Accounts and Import* tab
3. Alongside *Send email as:* you will find current signatures. You can delete, edit and change default here.