from The Century Dictionary.
- noun The act or process of labializing; conversion to a labial.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Phonetics) The modification of an articulation by contraction of the lip opening.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun linguistics A secondary articulatory feature of usually
consonantsthat involves the contractionor rounding of the labiaduring pronunciation.
from Wiktionary, Creative Commons Attribution/Share-Alike License
Maybe to add further, even without concommitant labialization, I don't think it's impossible that a pharyngeal to MIE ears would appear to have a +back acoustic quality, the same quality as their *w which may be one of the closest approximations they could make.
The other however generates a glottalic velar plus obvious labialization.
However, since Centralization and the concommitant transfer of labialization from the vowel to the neighbouring consonant is naturally heavily dependant on vocalism, I would have to oppose i-umlaut at the Proto-Steppe stage unless you can find a different formulation of Centralization that works to explain the rise of labialized consonants in PIE.
To me, *h3 was ultimately born from the era of Indo-Aegean Centralization when the feature of labialization was transferred to the neighbouring consonant, including *h.
So what I'm suggesting is what I like to call "disassociated labialization", or rather labialization remaining as residue a while after the phoneme to which its attached has eroded to null.
Word-final labialization was neutralized after Syncope, hence there were no instances in PIE, nor could there be, of suffixes like **-gʷ or **-hʷ **-h₃.
Either the labialization was absorbed there or the bilabial stops were lenited.
This might be called anticipatory labialization because you're anticipating the next sound, so subconsciously you begin to round your lips ahead of schedule.
In AbAd, palatalization (the act of pronouncing something with an added "y"-like quality) and labialization (the act of pronouncing something with an added "w"-like quality) are standard features in their sound systems.
At that point, palatalization and labialization could be understood as consonantal features.