Is it possible to update the values in the picklist using API?

Is it possible to update the values in the picklist using API?

Hello all,

Trying to get a definitive answer to the question:

"Is it possible to update the values of a picklists (in Accounts/Leads/Contacts/Events) using API?"
I'm not talking about Webform but the picklists that are used to enter data on the ZCrm Record when hit edit.

Thank you,
Erk