http://www.investopedia.com/terms/s/swinglineloan.asp#axzz1mu3uA8yQ Definition of 'Swingline Loan'
A loan that grants institutions access to large amounts of cash in order to cover possible shortfalls from other debt commitments.

Investopedia explains 'Swingline Loan'
You could compare this to a line of credit or demand loan, as a swingline loan gives companies immediate access to large sums of cash on short notice.