Stiff-neckedly is a word that is often used to describe someone who is stubborn or inflexible. It can be difficult to find synonyms for this term as it is quite specific in its meaning. However, some alternative ways of expressing this concept include phrases such as, 'resolutely', 'tenaciously', or 'doggedly'. These words convey a sense of determination and firmness of purpose, which is often associated with being stiff-necked. Additionally, other words that can be used to describe someone who is unwilling to bend or compromise include 'obstinate', 'intransigent', or 'unyielding'. These terms all evoke a sense of rigidity and unmovable will which is characteristic of a persona who is stiff-necked.