1. Messages or signals transmitted by heliograph (a device that uses mirrors to reflect sunlight for long-distance communication).
Usage: plural form; historical/military context; technical
2. Records or images produced by a heliograph or heliographic process.
Usage: plural form; archaic; photography/scientific

Examples

• The military unit sent heliograms across the desert to coordinate troop movements.
• During the 19th century, heliograms were an important means of long-distance communication in remote areas.
• The soldiers received heliograms from the distant outpost confirming the supply delivery.
• Early heliograms demonstrated the practical application of reflected sunlight for signaling.
• The commander decoded the heliograms transmitted from the mountain ridge.