Yes, you have to edit the XML for the action. Activate developer mode by going to help > About openERP > click active developer mode.

That will let you see the developer information. Then click edit action, and change the name of the action to what you want.

This will be over written when you update you database.

To do it properly you will have to inherit the XML view in a custom module and change the name in the <field name="name"></field> tag.

<record id="action_partner_form" model="ir.actions.act_window">
            <field name="name">Customers</field> <-- edit this to edit the name
            <field name="type">ir.actions.act_window</field>
            <field name="res_model">res.partner</field>
            <field name="view_type">form</field>
            <field name="view_mode">kanban,tree,form</field>
            <field name="context">{"search_default_customer":1}</field>
            <field name="search_view_id" ref="view_res_partner_filter"/>
            <field name="help" type="html">
              <p class="oe_view_nocontent_create">
                Click to add a contact in your address book.
              </p><p>
                OpenERP helps you easily track all activities related to
                a customer; discussions, history of business opportunities,
                documents, etc.
              </p>
            </field>