meist-

From meist (“most; mostly”).

• IPA^(key): /ˈmaɪ̯st-/

meist-

1. forms the superlative of past participles when this form is used to express frequency

   das meistgelesene Buch ― the most read book (read most often, by most people)

   der meistkritisierte Politiker ― the most criticized politician (criticized most often, by most people)

• Past participle superlatives that express a degree can be formed in the normal way, that is with the suffix -st: die zerstörteste Stadt (“the most destroyed city”). Alternatively, am meisten can be used before the positive form: die am meisten zerstörte Stadt. (The latter is only possible with participles.)
• There may be a semantic difference between a superlative with meist- and a normal superlative (though this is not the case with every past participle and generally is not often relevant in practice). Compare:

die zerstörteste Stadt (= die am meisten zerstörte Stadt) — the city that was most destroyed at a given point in time

die meistzerstörte Stadt (= die am häufigsten zerstörte Stadt) — the city that was most often destroyed in its history

• Double superlatives with both the prefix meist- and the suffix -st are not seldom encountered: das meistgelesenste Buch. This is regarded nonstandard usage in the formal register, but need not strike people as ungrammatical in informal use.