1. Two-way price quotations.
2. Borrowing and investment.
The differential between the yields on two fixed-income securities, usually expressed in basis points.
In the corporate borrowing context, it is usually the difference between the yield on a fixed-income corporate security, and a comparable risk-free investment, such as a gilt.
In statistics, spread is the extent to which data are clustered centrally, or more widely dispersed.
Measured for example by Standard deviation, Variance or Mean deviation.