S-shaped curve (4)
I believe the answer is:
ogee
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">s-shaped curve</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ogee that I've seen before include "Leer" , "S-shaped line" , "bit of Gothic architecture?" , "S-shaped moulding" , "architectural feature" .)