This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
滀 combines 氵 (water) with 畜, which likely contributes the sound. The exact historical development is uncertain.
Water 氵 beside 畜 suggests a gathering or pooling of water, perhaps like livestock gathering at a watering place. This fits the kun reading あつ.まる (to gather).
For チク, imagine water gathering in a thick pool: thick -> チク, and the water 氵 collects around 畜.