吃飯，吃起飯來。/打起電話來，打電話。/下起雨來，下雨。 They are the same in meaning for each pair of Chinese words. When doing something, the verb pluses the object should be used. When having done something and begining to do another thing, 動詞+起+object+來should be used. In this case 動詞+object also acceptable. When feeling hungry, you will go to eat(吃饭). When your meal is served, you begin to eat(吃起饭来or 吃饭). You call you mother every weekend. (打电话) You sat down and called you mother.（打起电话来or打电话） It is raining outside.(下雨) Is was shining moment ago, but now it begins to rain.(下起雨来or 下雨) Hope this helps.

You can say I am having my meal for your first word, you can say I am starting to have my meal for you second, the third is I am giving a call to somebody, the fourth is I want to give a call to somebody, the fifth is it is beginning to rain now, the last sentence is it has rained. Hope can help you, thank you!

when u describe something is just start ：外面下起雨来

when you use the pattern 動詞+起+object+來 it more like you are expressing a tone of progressive tense. ( past or present ) no matter 吃飯，打電話，or 下雨 it just a verb phrase.if translate these into english ,they will be: have a meal,make a call and rain. when you use these words in Chinese,people don't know when did (or will) these things happen,if you don't add a time . because, in chinese,if we want to express" he had a meal yesterday",we just add a word that means yesterday in the sentence,like "he have a meal yesterday" but translate 吃起飯來/打起電話來/下起雨來 into english they will be (sb) is (are /was/were) having a meal (sb) is (are /was/were) making a call it is (was) raining

吃饭，打电话，下雨 these three words describe that something happen or someone do sth ,however ,吃起饭来，打起电话来，下起雨来，these three phraeses mean someone start to do something or something start to happen,they empasize the action