<span class="searchmatch">propepsins</span> plural of <span class="searchmatch">propepsin</span> proppiness...
From pro- + pepsin. <span class="searchmatch">propepsin</span> (countable and uncountable, plural <span class="searchmatch">propepsins</span>) (archaic, biochemistry) pepsinogen “<span class="searchmatch">propepsin</span>”, in Webster’s Revised Unabridged...
for adults accustomed to full-sized horses than the 'proppiness' associated with the smaller (and indeed some of the larger) native breeds. <span class="searchmatch">propepsins</span>...