Senior Convertible Note

Senior: the most senior in a likely line of flavors of debt. It's followed by Junior Debt, maybe Subordinated Junior Debt, then just Debentures. Something like that.

But that Senior Note is convertible. Not into Catholicism. (We're out of Spain, 17th century.) Rather, it's likely convertible into common stock at some ratio. Like, one bond unit (par value $1,000) converts into 40 shares, so if the stock trades meaningfully above $25 a share, you'd want to convert it, and maybe just sell it and take your profits 'n' run.