"To contact a reference" means to reach out or communicate with someone who can provide information or vouch for another person's character, skills, or qualifications. Full definition
It's very unlikely that employers are contacting your references before even interviewing you; reference - checking usually takes place at the later stages of the hiring process. (careerdigital.com)
Upon request, say you will provide the list within 24 hours, allowing yourself time to contact the references in advance of the employer's call. (internships.com)
This report is compiled by contacting references for a business reference interview. (screen.careerbuilder.com)