USA
Debt (such as a bond or loan) is considered investment grade if its credit rating is BBB- or higher by Standard & Poor's or Baa3 or higher by Moody's or BBB or higher by Fitch. The term indicates that the debt being rated is of sound credit quality. Investment grade debt usually has more favorable terms and lower pricing for the borrower. The opposite of an investment grade bond is a speculative grade bond, also known as a junk bond.
Practical Law Dictionary. Glossary of UK, US and international legal terms. www.practicallaw.com. 2010.