打original meaning is hit, but when 打 combines with other word, the meanings are different. e.g.
relates to hit
打球 play ball
打架 fight
打人 hit someone
no hit at all:
(click the sentence to know the pronunciation and meaning)
打车/打的 to take a taxi 例如：我打车过来的。
打报告 reporting something to someone 例如：他向上司打报告。
打水 go to a canteen to get water using a container 例如：去饭堂打水。
打饭 go to a canteen to buy meal 例如：去饭堂打饭。
打针 get/give an injection 例如：他生病了，需要打针。
打毛衣 knitting 例如：她边看电视边打毛衣。
打电话 to make a phone call 例如：他正在打电话。
打扫 clean up 例如：打扫房间。
So, despite each single Chinese word has its clear meaning, but you'd better to read the compound word to figure out the specific meaning.
For the beginner it's not easy to conclude witch word is single word, which word is compound word because they all stick together. e.g.
他想出去散步半小时
他 想出 去散 步半 小时（incorrect）
他 想 出去 散步 半小时 (correct)。
There is no a certain way to distinguish single word or compound word except remember it one by one. Usually, noun and gerund are compound words, e.g. 电视，看电视；毛衣，打毛衣。
Don't be afraid, practice makes perfect.
#grammar, word