In Turkish, 'sık' generally means 'frequent,' 'dense,' or 'tight.' According to the TDK (Türk Dil Kurumu - Turkish Language Association), antonyms for 'sık' include words like 'seyrek' (sparse), 'nadir' (rare), or 'gevşek' (loose), depending on the context. For example, 'sık orman' (dense forest) would have an antonym of 'seyrek orman' (sparse forest). The specific antonym to use depends on the nuance of 'sık' being conveyed.