1. helpless/unable to function properly without someone/something
I'd be lost without someone
To be lost without somebody or something means that you are unhappy or unable to function properly without them or it. If talking about a person, this is a very emotive expression and means that the person being talked about is a key part of the person's life and if that were to change the would be hugely upsetting and disruptive. "I am so happy since I met my husband, I don't know what I would do without him." This expression can also be used in a casual way to talk about objects which are essential or very helpful. "This new program has automated so much of my administration work, I don't know what I would do without it."