(nautical) A mark on the hull of a merchant ship to show the waterline under specified conditions, indicating the maximum load that the ship may carry.

plural of International Load Line

A sport created as a mixture of Australian rules football and Gaelic football, to allow international matches between Australia and Ireland.

plural of international reply coupon

A prepaid international postage voucher.

Alternative form of internal combustion engine

Someone who is forced to flee his or her home but who remains within his or her country's borders. Abbreviated as IDP.

(optics, uncountable) A phenomenon where light, instead of passing into a medium of a lower refractive index and refracting away from the normal, is completely reflected by the boundary between the two media because it approaches at an angle greater than or equal to the critical angle.

(optics) total internal reflection

plural of total internal reflection