The teacher wrote down the words' pronunciations phonetically using phonetic symbols.

phonetically 是形容词 phonetic（语音的、音标的）加上副词后缀 -ally 构成的副词。phonetic 来自希腊语词根 phone（声音），表示与发音或语音相关的。phonetically 意思是"按照发音方式地、用音标符号地"。