One of the common requests we receive from clients looking to use JIRA for business process mapping, is to remove the Summary field. This is due to the fact that the term 'Summary' seems irrelevant to their business use case.
As this is a required JIRA field we do not recommend removing it (Plus JIRA has a bunch of built in functionality surrounding the 'Summary' field).
Any easy way to get around this is to have the Summary field populated by an other custom field. To make this a little more intuitive you will also want the 'Summary' fields default value set to text indicating that it will be auto-populated (ie. This field will be auto-populated by FieldX).
To begin you will want to ensure that you have defined a Field Configuration Scheme for the project that you will be implementing this functionality. In the field configuration add the following Javascript to the 'Summary' fields description (Open field configuration > edit field > insert in description):
<script type="text/javascript">
if (document.getElementById("summary").value == "") {
document.getElementById("summary").value = "Value auto-populated from FieldX\n";}
</script>