XLB Views 6 meanings found XLB is best known as the file extension for Microsoft Excel worksheets and as ticker symbols for major investment funds like the Materials Select Sector SPDR and iShares bond fund. Miscellaneous Extra Large for Boys Regional Lac Brochet Airport, Lac Brochet, Monitoba, Canada Computing Excel Worksheet X11 application Launch Bar Business Materials Select Sector SPDR iShares DEX Long Term Bond Index Fund