Undulation (4)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">undulation</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for wave that I've seen before include "may have a crest at the top?" , "Shake a hand in the air" , "Undulating curve" , "Move hand to and fro as greeting" , "60s cinematic movement with 1a [NEW]" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">undulation</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that ripple is a type of oscillation)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ripple that I've seen before include "A small wave, or a gentle sound as of laughter" , "Slight surface wave" , "Small wave on a liquid's surface" , "undulation" , "Small wave or surface disturbance" .)