diff --git a/zulip_bots/zulip_bots/bots/define/define.py b/zulip_bots/zulip_bots/bots/define/define.py
index 69d9722..6f0ea83 100644
--- a/zulip_bots/zulip_bots/bots/define/define.py
+++ b/zulip_bots/zulip_bots/bots/define/define.py
@@ -3,6 +3,7 @@ import logging
 import json
 import requests
 import html2text
+import string
 
 class DefineHandler(object):
     '''
@@ -14,6 +15,7 @@ class DefineHandler(object):
     REQUEST_ERROR_MESSAGE = 'Could not load definition.'
     EMPTY_WORD_REQUEST_ERROR_MESSAGE = 'Please enter a word to define.'
     PHRASE_ERROR_MESSAGE = 'Definitions for phrases are not available.'
+    SYMBOLS_PRESENT_ERROR_MESSAGE = 'Definitions of words with symbols are not possible.'
 
     def usage(self):
         return '''
@@ -36,6 +38,11 @@ class DefineHandler(object):
         to_define = split_content[0].strip()
         to_define_lower = to_define.lower()
 
+        # Check for presence of non-letters
+        non_letters = set(to_define_lower) - set(string.ascii_lowercase)
+        if len(non_letters):
+            return self.SYMBOLS_PRESENT_ERROR_MESSAGE
+
         # No word was entered.
         if not to_define_lower:
             return self.EMPTY_WORD_REQUEST_ERROR_MESSAGE
diff --git a/zulip_bots/zulip_bots/bots/define/test_define.py b/zulip_bots/zulip_bots/bots/define/test_define.py
index 71b5f6e..614e00c 100755
--- a/zulip_bots/zulip_bots/bots/define/test_define.py
+++ b/zulip_bots/zulip_bots/bots/define/test_define.py
@@ -58,6 +58,14 @@ class TestDefineBot(BotTestCase):
             expected_method='send_reply'
         )
 
+        # Symbols are considered invalid for words
+        bot_response = "Definitions of words with symbols are not possible."
+        self.assert_bot_response(
+            message = {'content': '#'},
+            response = {'content': bot_response},
+            expected_method='send_reply'
+        )
+
         # Empty messages are returned with a prompt to reply. No request is sent to the Internet.
         bot_response = "Please enter a word to define."
         self.assert_bot_response(