The origins of lambaste are somewhat uncertain, but the word was most likely formed by combining the verbs lam and baste, both of which mean to beat severely. (Incidentally, lambaste can also be spelled lambast, despite the modern spelling of the verb baste.) Some other synonyms of lambaste include pummel, thrash, and pound.
According to the Wikipedia article on Fahrenheit: Fahrenheit remains the official scale for the following countries: the Bahamas, Belize, the Cayman Islands, Palau and the United States and associated territories (Puerto Rico, Guam and the U.S. Virgin Islands). Canada retains it as a supplementary scale that can be used alongside Celsius.
If you're familiar with the verb to indicate, then indicator should be no problem. An indicator points to, suggests, or shows something. The arrow on a street sign is an indicator telling you which way to go. In other words, temperature is only one indicator of how it feels outside. Air-pressure, humidity, wind-chill, and cloud cover are other important indicators of weather conditions. You might hear a lot from newscasters about economic indicators..