Extracts from the leaves of the Bangladeshi medicinal plant Terminalia citrina were prepared, and 13 new furofuran lignan glucosides, terminalosides A-K (1-4, 6-12), 2-epiterminaloside D (5), and 6-epiterminaloside K (13), were characterized using various spectroscopic techniques. Twelve of the isolates were found to contain rare tetraoxygenated aryl groups in their structures. Analysis of the NMR chemical shifts for the oxymethine signals in the furofuran ring suggested a pragmatic approach to determining the relative configuration of these compounds. The ECD and NOESY spectroscopic data obtained allowed for the deduction of the absolute configurations and conformations of the compounds. The isolates were tested for their estrogenic/antiestrogenic activity using the MCF-7 and T47D estrogen-responsive human breast cancer cell lines. Terminalosides B (2) and G (8) exhibited inhibitory effects for both cell lines, and estradiol-enhanced cell proliferation was suppressed by 90% at concentrations lower than 10 μM. Terminaloside E (6) showed inhibitory activity against the T47D cell line, whereas terminalosides C (3), F (7), and I (10) and 6-epiterminaloside K (13) displayed antiestrogenic activity against MCF-7 cells.