‘Senior Secured’ is market convention terminology that means a bond has a first right to assets of the company over unsecured creditors in the event of a liquidation. Assets may include property, equipment, cash, and intellectual property. 

This means that if for any reason security over the company is enforced by lenders, senior secured bond holders will receive proceeds with first priority to any junior or subordinated debt holders and until the principal amount of the senior secured loan or bond has been repaid. However assets of the company may still not be enough to ensure a full recovery for senior secured bond holders in the event of a company liquidation.