The word "hardboot" can have different meanings, depending on the context where it is being used. If it pertains to a ski or snowboard equipment, some synonyms that can be used are "alpine boot" or "race boot." Meanwhile, if the word refers to a computer system's startup process, some alternate phrases that can be used are "cold boot" or "physical boot." For someone who is being strict or inflexible, some words that can be used are "rigid," "unbending," or "inflexible." Meanwhile, for something that is difficult to do or accomplish, some synonyms that can be used are "challenging," "demanding," or "arduous".