moody, cranky, someone with rapidly changing moods
Building blocks
tuju- - temper/mood
-kas - an adjective-forming ending (when added to a noun it shows an abundance of a quality)
So in this case it creates an adjective that describes someone who is in “abundance of moods” aka someone “moody”.
How to use it:
Describing someone's temperament:
"Ta on täna eriti tujukas." (He/she is particularly moody today.):
Describing the quickly changing weather conditions:
"Sel sügisel on olnud eriti tujukas ilm.” (This autumn, the weather has been particularly moody.)
Examples
Järgnevatel päevadel on ilm üpris tujukas
Literally: “Following-on days-on is weather rather moody”
Idiomatically: “In the following days the weather is rather moody”
Järgnevatel - Adjective - Adessive Pl, "Following-on"
päevadel - Noun - Adessive Pl, "days-on"
on - Verb - 3P Present Sg, "is"
ilm - Noun - Nominative Sg, "weather"
üpris - Adverb - Indeclineable, "rather"
tujukas - Adjective - Nominative Sg, "moody"