# import necessary libraries
import pandas as pd

# define your series
series = pd.Series(['apple', 'banana', 'cherry', \
                    'plum', 'orange'])

# create custom function
def has_two_vowels(word):
    word = word.lower()
    vowels = [char for char in word \
              if char in 'aeiou']
    if len(vowels) >= 2: return word 

# use apply() to apply the function
words = series.apply(has_two_vowels).dropna()

# print filtered words
print(words.to_list())