The word Trööt appears in the title of the article “Bundesregierung im Fall Yücel. Protest ohne Trööt.” from Der Spiegel.
For context purposes, here is the introductory paragraph of the article:
Der deutsch-türkische Journalist Deniz Yücel sitzt in der Türkei in U-Haft: Die Kanzlerin zeigt ihre Enttäuschung, Außenminister Gabriel bittet den türkischen Botschafter zum Gespräch. Sind damit ihre Möglichkeiten schon erschöpft?
The word Trööt is not listed in any of the online dictionaries in which I looked it up (dict.cc; dict.leo.org, en.pons.com, dictionary.reverso.net, duden.de).
So, first question, what does the word Trööt mean?
And, second question, are there any other German words with two consecutive umlaut letters? My memory may be failing me, but I don't remember seeing two consecutive umlaut letters in any of the other German words that I came across during the past three years of reading the German press.