sa'ei zei valsi zei-lujvo

x1 is an onomatopoeia, a word that sounds like what it represents

Examples are "gurgle" or "hiss". See sa'ei, ki'ai, valsi

On affix form:

valsi
x1 is a word meaning/causing x2 in language x3; (adjective: x1 is lexical/verbal).
zekri
x1 (event/state) is a punishable crime/[taboo/sin] to people/culture/judges/jury x2.

In definition:

cmapagjvo
x1 (text) is a lujvo with meaning x2 and arguments x3, and which is constructed from tanru/veljvo x4 such that each element of the veljvo is ultimately only a cmavo (including "{zei}", "{ke}"/"{ke'e}", "{bo}", etc.), gismu, or rafsi of such cmavo or gismu.
zejvo
x1 (text) is a Lojban compound predicate using the particle “zei”; with meaning x2, arguments x3, built from metaphor (tanru) x4.
luvrzei
x1 (text) is a Lojban compound predicate using the particle “zei”; with meaning x2, arguments x3, built from metaphor (tanru) x4.
zeiljvo
x1 (text) is a Lojban compound predicate using the particle “zei”; with meaning x2, arguments x3, built from metaphor (tanru) x4.
zo si si zei fa'o
x1 is a nonsense zei-lujvo using parts x2, silly by standard x3.

In notes:

snafu'ivla
x1 is an onomatopoeic word meaning x2 in language x3, based on sound x4 emitted by x5
bi'au (exp!)
attitudinal: bzz, bee/other insect sound
ci'oi (exp!)
Converts following cmevla or zoi-quote into psychomime.
ki'ai (exp!)
Converts following selbri, cmevla, or zoi-quote into a nonce interjection/attitudinal.
mi'au (exp!)
attitudinal: meow, miaow
tai'i (exp!)
Converts following cmevla or zoi-quote into phenomime.
isku
x1 is a sound represented by onomatopoeia x2 (text) according to x3 (experiencer)