Initialism of Random House Dictionary of the English Language Unabridged.

(space science, robotics) Initialism of radioisotope heater unit. (a device that generates heat from the natural decay of radioactive material)

plural of RHU

A village west of Helensburgh in Argyll and Bute council area, Scotland (OS grid ref NS2684).

Synonym of sumacade

(navigation) A line which crosses successive meridians at a constant angle / (navigation) One of the 32 points of the compass (compass points)

Any plant of the genus Rheum, especially Rheum rhabarbarum, having large leaves and long green or reddish acidic leafstalks that are edible, in particular when cooked (although the leaves are mildly poisonous).

Of the colour of rhubarb: either brownish-yellow (the colour of rhubarb rhizomes and roots used for medicinal purposes), or pale red (often the colour of the leafstalks of common rhubarb).

(Britain, military, aviation) Of fighter aircraft: to fire at a target opportunistically.

(originally theater, uncountable) General background noise caused by several simultaneous indecipherable conversations, which is created in films, stage plays, etc., by actors repeating the word rhubarb; hence, such noise in other settings.