This is a possible solution to a boggle board matrix in ruby.

BoggleSolution.rb

# It should be noted that the OP requested this to
# work in a way that allows for ANY combination of
# words, not just the Boggle Standard rules
def include?(word)
  word.upcase!
  board.flatten!

  word.each_char do |c|
    return false unless board.include?(c)
    board.delete_at(board.index(c))
  end
  
  true
end

BoggleSolutionComments.rb

def include?(word)
  # Make the word upcase so we don't have to worry about incorrect casing in the include
  word.upcase!
  # flatten the multi dimentional array so we can easily use .include? on it
  board.flatten!

  # use each_char on our word, which c will give us one character of our word one by one.
  # i.e. "test" will give us t, e, s, and t one at a time
  word.each_char do |c|
    # The next statement is pretty readable as is, but I'll flip it:
    # if board doesn't include the character I'm currently iterating,
    # kill the loop and return false to the overall function
    return false unless board.include?(c)
    
    # We got past the include check!
    # Delete *1* of the characters that we "used", since each
    # boggle board character can only be used once.
    board.delete_at(board.index(c))
  end
  
  # Every character provided had a returned value, return true:
  true
end