wow, I am very impressed with everyone's answers! Now I know 一头热! I looked up the dictionary, there were other words for one sided love, 单恋 and 单相思. These are more commonly used ? but I kind of like 一头热 the best for some reason :)

As anita said, 一頭熱 means to be hot at one end, and it's actually the second part of a longer expression: 剃頭擔子一頭熱。And sjzh pretty much has the answer. 剃頭 means to shave one's head, but here it's placed in front of another noun 擔子 and is used as an adjective meaning head-shaving. So 剃頭擔子 means a head-shaving 擔子. But what is a 擔子? To know 擔子, you will have to know 扁擔 first. A 扁擔 is a long half-split piece of bamboo which is placed over your shoulder and used as a carrying device. Since the bamboo is split, it's not round anymore; therefore 扁 (meaning flat). And it's placed over your shoulder; therefore 擔 (the meaning of this noun derives from when it's used as a verb meaning to shoulder). For better understanding, here's a link to a picture of 扁擔： http://www.flickr.com/photos/revoldrib/499325407/ Now that you know what a 扁擔 is, it's easier to understand 擔子. A 扁擔 along with the goods/items it carries is called a 擔子. To this day we still say something like 我肩上擔子很重 to mean the responsibility we carry is heavy. So what's with 剃頭擔子? A 剃頭擔子 is carried by a shaver/barber and normally has hair-shaving/cutting stuff on one end, and a container of hot water for cleansing on the other; therefore, only one side of the 擔子 is hot. Somehow the idea of a 剃頭擔子 being only hot on one end is extended to describe a relationship where one side is indifferent and the other is very much devoted. 一頭熱 is like a punch line giving away the answer to what 剃頭擔子 means here. Finally, 對感情一頭熱 means to be one-sidedly devoted in love.

I love you, affectionately, but you don't love me at all. 那我我对你的爱就是"一头热".

對 means to / toward / for, a preposition. 一頭 means an end / one side, not a head. the pattern of 一頭熱 should not be interpreted as number + classifier + noun. 一頭熱 means to be hot at one end. 一頭熱 比喻一廂情願 如「這只是他一頭熱，對方連一點意思都沒有。」 for more information on the phrase 一頭 , please refer to http://dict.revised.moe.edu.tw/cgi-bin/newDict/dict.sh?idx=dict.idx&cond=%A4@%C0Y&pieceLen=50&fld=1&cat=&imgFont=1 重編國語辭典修訂本 中華民國教育部　版權所有

對感情一頭熱= Love caught inside still have any questions.visit,http://www.echineselearning.com/free-trial/index.html?ecl=ptEEEEEEit112501 Take a Free 1-on-1 live online lesson with our professional teachers from China.