1. half-long - Noun
2. half-long - Adjective
half-long (not comparable)
Between a short vowel and a long vowel in length.
half-long (plural half-longs)
A vowel that is between a short vowel and a long vowel in length.
Synonym: half-long vowel
Particularly, the half-long vowels (found in word-final codaless single-vowel syllables) are lengthened into full-blown long vowels, as in iso → isoo. Source: Internet
The Mixe language has a three-way contrast among short, half-long, and long vowels, and this has been reported for a few other languages, though not always as a phonemic distinction. Source: Internet