Approximant

An approximant is a sound that is produced by a slight narrowing of the vocal tract, but not enough to cause noise or a complete obstruction.

Examples
The semivowels [j], [w] and the English r.

Origin
Approximants are so called because in their production, the active articulator approximates (=comes close to) the passive articulator.

Other languages
German Approximant (de)

Link
Utrecht Lexicon of Linguistics