what do sumo hand gestures mean?

The wrestler take his hand and palm vertical, moves it to the left then the right and then in the middle -then he picks up his prize money.

I think this may explain it all for you.

http://www.lemondedusumo.com/english/MDS3_description_bout.html

I think this may explain it all for you.

http://www.lemondedusumo.com/english/MDS3_description_bout.html

Basically above explanation in EN is corret.
http://sumokenkyu.blog.fc2.com/blog-entry-112.html

More details :
That action is one of "手刀(shutou/tegatana)".
手(te) means "hand", 刀(katana) is "sword".
手刀 makes the border cuts btw real life and God area.
Money is real life's one, so they say "Thanks!" to "Three Gods" of harvest "by hand".

Three Gods(神/kami) :
左(left) : 神産巣日神（かみむすびのかみ）Kamimusubi no kami
右(right): 高御産巣日神（たかみむすびのかみ） Takamimusubi no kami
中(mid) : 天御中主神（あめのみなかぬしのかみ）Amenominakanushi no kami
https://en.wikipedia.org/wiki/Kotoamatsukami

Some Sumo players(力士: rikishi) doing "fourth" action after money recieved,
they writting the word "心(kokoro)/mind,heart" of Kanji.
https://en.wiktionary.org/w/index.php?title=%E5%BF%83&oldid=42470856
But 心's stroke order is just move left to right no back to mid part.
This is same meaning alternative form calling "risshin-ben" strokes.
http://dict.v01.jp/utf_image.php?q=5FC4
https://en.wiktionary.org/w/index.php?title=%E5%BF%84&oldid=41634454

Anyway, that action is one of "御祓い/oharai = purification ritual in Shinto.

Japanese sign lang "Thank you!" action is coming from this Sumo action.
https://youtu.be/52Jk063HMtk

Thanks SO much for explaining this.
I'm watching the NHK highlights of this tournament and it was something I was wondering about, so you've done me a favour even though I'm not the OP.

Sorry for sidetrack, but I want to say those Sumo wrestlers are awesome! I have never seen an actual bout till NHK highlights. All along i thought they are just fat, but I was so wrong. There's some serious muscle under that layer of lipids and they sure can move fast.