A kangaroo word is a word that contains letters of another word, in order, with the same meaning. For example: the word masculine contains the word male, which is a synonym of the first word; similarly, the word observe contains its synonym see.
Etymology
The etymology of the phrase kangaroo word is from the fact that kangaroos carry their young (known as joeys) in a body pouch. Likewise, kangaroo words carry their joey words within themselves. Twin kangaroos are kangaroo words containing two joey words (for example: container features both tin and can). In contrast, an anti-kangaroo word is a word that contains its antonym; for example: covert carries overt, animosity carries amity.
Some compilers require that the letters of the joey word not be consecutive within the kangaroo word, or that the kangaroo and joey words must be etymologically unrelated.
Kangaroo words were originally popularized as a word game by Ben O'Dell in an article for The American Magazine, volume 151, during the 1950s. This was later reprinted in the Reader's Digest.