Render mixture plain text and HTML output from a command in a terminal

Use a text mode browser such as w3m or lynx. Strip off the non-HTML prefix, and tell the browser that this is HTML (lynx assumes it, but w3m doesn't, because this is an HTML snippet, not a full document). Tell the browser to dump to screen rather than show an interactive interface.

$ /usr/bin/sdcv counterpart | awk '/^</ {p=1} p' | w3m -T text/html -dump
◆ counter|part /k'aʊntə^rpɑː^rt/ (counterparts)
[N-COUNT] with supp, usu poss N
Someone's or something's counterpart is another person or thing that has a
similar function or position in a different place.
● The Foreign Secretary telephoned his Italian counterpart to protest.

$ /usr/bin/sdcv counterpart | awk '/^</ {p=1} p' | lynx -stdin -dump
   ◆ counter|part /k'aʊntə^rpɑː^rt/ (counterparts)
   [N-COUNT] with supp, usu poss N
   Someone's or something's counterpart is another person or thing that
   has a similar function or position in a different place.
   ● The Foreign Secretary telephoned his Italian counterpart to protest.
     __________________________________________________________________

I have solved the problem with pandoc and elinks: save output(stdout) as markdown file, then use pandoc render md to html file, render local html file with elink -dump finally. Below is my script:

#tt.sh
/usr/bin/sdcv $1 > /home/czxyl/Documents/firstlove.md
pandoc /home/czxyl/Documents/firstlove.md -o /home/czxyl/Documents/firstlove.html
elinks -dump /home/czxyl/Documents/firstlove.html
rm /home/czxyl/Documents/firstlove.html /home/czxyl/Documents/firstlove.md

alias def='. tt.sh'

# czxyl @ archlinux in ~ [0:22:34] 
$ def hello
   Found 7 items, similar to hello. –>CMU American English spelling –>hello

   [hə’ləu]

   –>dictd_www.dict.org_gcide –>Hello

   Hello lo“, interj. & n. An exclamation used as a greeting, to call
   attention, as an exclamation of surprise, or to encourage one. This
   variant of {Halloo} and {Holloo} has become the dominant form. In the
   United States, it is the most common greeting used in answering a
   telephone. [1913 Webster +PJC]

   –>WordNet –>hello

   hello n : an expression of greeting; “every morning they exchanged polite
   hellos” [syn: {hullo}, {hi}, {howdy}, {how-do-you-do}]

   –>Webster’s Revised Unabridged Dictionary (1913) –>Hello

   Hello lo“, interj. & n. See {Halloo}.

   –>牛津现代英汉双解词典 –>hello

   = hallo.

   –>Longman Dictionary of Contemporary English –>hello

   S1 interjection, n also hallo, hullo BrE [C] [Date: 1800-1900; Origin:
   hollo a shout to call attention (16-19 centuries)]// 1 used as a greeting
   when you see or meet someone: –Hello, John! How are you?// –Stanley, come
   and say hello to your nephew.// –Well, hello there ! I haven’t seen you
   for ages.// 2 used when answering the telephone or starting a telephone
   conversation: –Hello - may I speak to Anne?// 3 used when calling to get
   someone’s attention: –Hello! Is there anybody home?// 4 used when you
   think someone is not acting sensibly or has said something stupid: –You
   didn’t remember her birthday? Hello!// 5 BrE used to show that you are
   surprised or confused by something: –Hello! What’s happened here?// 6 say
   hello: to have a quick conversation with someone// –Promise you’ll look in
   and say hello when you have time.//

   –>Collins Cobuild 5 –>golden hello

   gold|en hel|lo (golden hellos)
   [N-COUNT]
   A golden hello is a sum of money that a company offers to a person in
   order to persuade them to join the company. (BUSINESS)
   ● Most people recognise the need to pay a golden hello to attract the
   best.

   ══════════════════════════════════════════════════════════════════════════

# czxyl @ archlinux in ~ [0:22:40] 
$