密度波

density wave

secret / confidential / close / thick / dense

density / thickness

to pass / to spend (time) / measure / limit / extent / degree of intensity / degree (angles, temperature etc) / kilowatt-hour / classifier for events and occurrences

to estimate / Taiwan pr. [duo4]

Poland / Polish / abbr. for 波蘭|波兰[Bo1 lan2]

wave / ripple / storm / surge