Bahubbiihi compounds are adjectival compounds whose posterior words
are always nouns. These compounds also always have an exocentric
focus. This means that they refer to an outside object and must be
understood in relation to that object in order to be fully comprehensible.
One example of an English sentence using a compound of this type is:
"Hey big-mouth, get over here!"
"Big-mouth" in this case obviously does not literally refer to a
"big-mouth" that someone is calling, but to a person who HAS a
"big-mouth," or more specifically, a person who talks too much or too
loudly. The referent in this case is a person, and thus even though
"big-mouth" is a noun, it is qualifying the referent which is a person
and is hence acting as an adjective.
Thus, this compound "big-mouth" is an adjective qualifying a person,
and must be understood as such since it functions as a noun in the
sentence. To gloss the term "big-mouth" as literally referring to a
big mouth would be a mistake and the resulting translation would be
quite incorrect.
One may note that "big-mouth" is in fact formed just like a
kammadhaaraya compound and the only thing that makes it a bahubbiihi
is the context. As a bahubbiihi it is acting as an adjective of the
referent that is not included in the compound itself. If we were
indeed speaking of a big mouth such as in the phrase: "wow, look at
that big-mouth" and we literally meant that there was a really big
mouth that were looking at, then it would simply be a kammadhaaraya in
the form of (adj+substantive).
This rule applies to other bahubbihi compounds which may be formed as
tappurisa compounds (or the other types of compounds for that matter)
such as "baby-face" where the case relation is genitive between the
members, i.e., "face of a baby," yet if we were to speak to an adult
thusly: "Hey baby-face, get over here!" then this compound that is
formed as a tappurisa would be used as a bahubbiihi compound and thus
would function as an adjective related to the referent which is not
specifically mentioned here(the adult). In sentences with bahubbiihi
compounds, however, the referent may be either stated or implict.
An example of a bahubbihi in Paa.li would be in the following phrase:
"ka.nhadanta.m passaami" = I see "black-tooth."
In this case, black-tooth is not a black tooth that someone sees, but
a person whose single tooth (or perhaps plural) is black (or very
dark) and is therefore referred to as "black-tooth." If we wanted to
really specify the referent, we would have to translate this as: "I
see [the person] who has the black tooth(/teeth)."
Thus, because "black-tooth" refers to a non-present referent in this
sentence, it is adjectival and a bahubbiihi. Additionally, as
explained above, we can see that this bahubbiihi is formed as a
kammadhaaraya type 1 as explained above, i.e. adj+substantive.