Hidden inside arco sit acro, arco, and orca, four-letter plays tied at the top of this rack with 6 points in Scrabble apiece. In all, 14 valid words come out of this rack, grouped by length below and checked for Words With Friends as well as Scrabble.
acro, arco, and orca tie for the highest Scrabble score from arco at 6 points. The top 10 of 14 words are shown here, with the full list organized by length below.
There are 3 four-letter words hiding in arco: two come from rearranging its letters, and arco itself is already a playable word with no unscrambling required. No common everyday answer stands out among these four-letter results, so let the score decide: the highest-scoring words are acro, arco, and orca, each worth 6 points in Scrabble.
Swap a single tile in arco and you get a different four-letter rack with its own word list. None of these appear in the results above — they share 3 of the 4 letters, not all of them.
arco is in the NWL, the official Scrabble word list for North America, and in the Words With Friends dictionary, so it's playable exactly as it stands and needs no unscrambling.
The 1-point gap between the two totals comes from the tile values themselves: Scrabble and Words With Friends price the same letters differently.
Dictionaries record one sense for arco. Scrabble and Words With Friends score tiles and not meanings, so every sense below is worth the same 6 points on a Scrabble board:
arco is one of three four-letter words the same letters produce. No arrangement of the same tiles scores higher in Scrabble, so playing arco unchanged also takes the maximum points these letters offer.
The highest-scoring plays from these letters are acro, arco, and orca, worth 6 points in Scrabble, and nothing else built from arco earns more points in Scrabble. Words With Friends prices the same letters differently, so the top of the list changes on a Words With Friends board. Both scores count tile values only and exclude premium squares.
The letters in arco produce 14 valid words in the Scrabble and Words With Friends dictionaries. The word count by length is: 3 four-letter words, 9 three-letter words and 2 two-letter words.