On gloss:

tavla in sense "any speech"
x1 talks/speaks to x2 about subject x3 in language x4.
baupli in sense "to speak a language"
x1 uses language x2 for purpose x3.

In definition:

casnu
x1(s) (mass normally, but 1 individual/jo'u possible) discuss(es)/talk(s) about topic/subject x2.
banbau
b1 is a metalanguage used by b2 to talk about object language b3.
cifku'ita'a
k1=t1 is/are using baby talk/caretaker speech/infant-directed speech (IDS)/child-directed speech (CDS)/parentese to c1=k2=t2 (default: infant/baby) about subject t3 in language t4.
donta'a
x1 talks to you (i.e. whoever x1 is addressing) about x2 in language x3
fonta'a
t1 talks on the phone to t2 about t3 in language t4.
guglypevgri
x1 is a Google Group for x2 to discuss/talk about subject x3
guglyzamgri
x1 is a Google Group for x2 to discuss/talk about subject x3
jbosnu
c1 (mass normally, but 1 individual/jo'u possible) discuss(es)/talk(s) about topic/subject c2 in Lojban.
jbota'a
x1 talks/speaks in Lojban to x2 about subject x3
kibysnustu
s1 is a Internet forum for c1 to discuss/talk about topic/subject c2.
samta'a
t1 talks via computer to t2 about t3 in language t4.
sezyta'a
x1 talks to himself/herself/themselves about x2 in language x3
snustu
s1 is a forum for c1 to discuss/talk about topic/subject c2.
ta'asku
x1 (entity) talks about x2 (entity) to x3 (entity); x1 (entity) speaks to x3 (entity) about x2 (entity)
ta'avru
x1 is talking noise / background chatter to x2 observed via senses x3 of x4 talking to x5 about x6 in language x7.
tavmu'o
x1 has finished talking to x2
tavysi'u
x1 talk to each other about x2 in language x3
vlaxagji
x1=xa1 is hungry to talk about x2 using words in language x3=v3. In other words, x1=xa1 wishes there existed useful words for x2 in the language x3=v3.
jborefota
x1 is a pair of Lojbanists who frequently talk to each other in Lojban by telephone.
konfabu
x1 (group) confabs, confabulates, talk socially about x2 without intentionally exchanging much information
mlauca
x1 mentions or alludes to x2 while talking to x3
gugyl zei zamgri
x1 is a Google Group for x2 to discuss/talk about subject x3

In notes:

sepli
x1 is apart/separate from x2, separated by partition/wall/gap/interval/separating medium x3.
xanri
x1 [concept] exists in the imagination of/is imagined by/is imaginary to x2.
doinai (comp!)
"anti-vocative": specifically denies that the referent is the intended listener.
ba'usku
s1=b1 (agent) says s2=b2 (sedu'u/text/lu'e concept) for audience s3 through expressive medium s4.
clacinlygruslanu
x1 is a long, thin, grainish cylinder (also known as spaghetti) of grain species g2
crebi'o
c1=b1 becomes expert at c2=b2 under conditions b3 by standard c3.
mafta'a
x1 and x2 magictalk about x3
sizyjvomi'u
x1 is the concept/idea of lujvo-equivalence, as held by x2
terbripaubri
x1=bP1=p1 is a subordinate clause relation / abstraction relation with predicate x2=bP2 and arguments x3=bP3, among the arguments x4=p2=bZ3 of relation x5=bZ1.
velseljvo
x1 is the (underlying/originating) construct (usually tanru) of lujvo/compound x2 with terbri/structure x3 and meaning x4
tubra
x1 is a limb/appendage/extremity of body/entity x2 used for purpose x3
bo'a
pro-sumti: definitional terbri variable 1; x1
bo'e
pro-sumti: definitional terbri variable 2; x2
bo'i
pro-sumti: definitional terbri variable 3; x3
bo'o
pro-sumti: definitional terbri variable 4; x4
bo'u
pro-sumti: definitional terbri variable 5; x5
cau'o'e (exp!)
elliptical/vague/indecisive scalar affirmer/negator; true neutral/non-committed/uninvolved scalar truthfulness/assertion.
dai'i
attitudinal modifier: supposed emotion - factual emotion
xe'o (exp!)
discursive: simply/merely/just, "all there is to it" - not simply, not just, "there's more to it"
jbovaseji
x1 adds x2 to Lojban dictionary x3 (default la jbovlaste)
su'umdu
x1 is the predicate abstraction described by text x2, and is of type x3
tcasnuue
x1 (nu) is a conversation/dialogue/exchange/scene/series of communicative responses/series of expressions/series of messages/exchange of information event between participating speakers x2 (ordered list; ce'o) and passive or active audience members x3 (set; may repeat elements of x2) in languages x4 (use "fa'u" if desired) and via expressive media x5 (use "fa'u" if desired) in which the following utterances/messages/expressions are, in/according to frame of reference x6, made/sent or received in approximately the following chronological order: x7 (sedu'u/text/quote/lu'e concept vel sim.), x8 (sedu'u/text/quote/lu'e concept vel sim.), x9 (sedu'u/text/quote/lu'e concept vel sim.), ... (open-ended terbri structure of arbitrarily many sumti slots).
tcaudu
x1 is the formatted address for something - (with format) starting with x2, which is an address/locality/administrative subunit/region which belongs to slightly broader address/locality/administrative subunit/region x3, which in turn itself belongs to a slightly broader address/locality/administrative subunit/region x4, \dots (etc.).